This is /home/jwe/src/octave-stable/doc/interpreter/octave.info, produced by makeinfo version 4.13 from /home/jwe/src/octave-stable/doc/interpreter/octave.texi.

START-INFO-DIR-ENTRY
* Octave: (octave).           Interactive language for numerical computations.

END-INFO-DIR-ENTRY

   Copyright (C) 1996, 1997, 1999, 2000, 2001, 2002, 2005, 2006, 2007,
2011 John W. Eaton.

   Permission is granted to make and distribute verbatim copies of this
manual provided the copyright notice and this permission notice are
preserved on all copies.

   Permission is granted to copy and distribute modified versions of
this manual under the conditions for verbatim copying, provided that
the entire resulting derived work is distributed under the terms of a
permission notice identical to this one.

   Permission is granted to copy and distribute translations of this
manual into another language, under the above conditions for modified
versions.


File: octave.info,  Node: Hashing Functions,  Prev: System Information,  Up: System Utilities

36.12 Hashing Functions
=======================

It is often necessary to find if two strings or files are identical.
This might be done by comparing them character by character and looking
for differences.  However, this can be slow, and so comparing a hash of
the string or file can be a rapid way of finding if the files differ.

   Another use of the hashing function is to check for file integrity.
The user can check the hash of the file against a known value and find
if the file they have is the same as the one that the original hash was
produced with.

   Octave supplies the `md5sum' function to perform MD5 hashes on
strings and files.  An example of the use of `md5sum' function might be

     if exist (file, "file")
       hash = md5sum (file);
     else
       # Treat the variable "file" as a string
       hash = md5sum (file, true);
     endif

 -- Loadable Function:  md5sum (FILE)
 -- Loadable Function:  md5sum (STR, OPT)
     Calculate the MD5 sum of the file FILE.  If the second parameter
     OPT exists and is true, then calculate the MD5 sum of the string
     STR.


File: octave.info,  Node: Packages,  Next: Dynamically Linked Functions,  Prev: System Utilities,  Up: Top

37 Packages
***********

Since Octave is Free Software users are encouraged to share their
programs amongst each other.  To aid this sharing Octave supports the
installation of extra packages.  The `Octave-Forge' project is a
community-maintained set of packages that can be downloaded and
installed in Octave.  At the time of writing the `Octave-Forge' project
can be found on-line at `http://octave.sourceforge.net', but since the
Internet is an ever-changing place this may not be true at the time of
reading.  Therefore it is recommended to see the Octave website for an
updated reference.

* Menu:

* Installing and Removing Packages::
* Using Packages::
* Administrating Packages::
* Creating Packages::


File: octave.info,  Node: Installing and Removing Packages,  Next: Using Packages,  Up: Packages

37.1 Installing and Removing Packages
=====================================

Assuming a package is available in the file `image-1.0.0.tar.gz' it can
be installed from the Octave prompt with the command

     pkg install image-1.0.0.tar.gz

If the package is installed successfully nothing will be printed on the
prompt, but if an error occurred during installation it will be
reported.  It is possible to install several packages at once by
writing several package files after the `pkg install' command.  If a
different version of the package is already installed it will be
removed prior to installing the new package.  This makes it easy to
upgrade and downgrade the version of a package, but makes it impossible
to have several versions of the same package installed at once.

   To see which packages are installed type

     pkg list
     -| Package Name  | Version | Installation directory
     -| --------------+---------+-----------------------
     -|        image *|   1.0.0 | /home/jwe/octave/image-1.0.0

In this case only version 1.0.0 of the `image' package is installed.
The '*' character next to the package name shows that the image package
is loaded and ready for use.

   It is possible to remove a package from the system using the `pkg
uninstall' command like this

     pkg uninstall image

If the package is removed successfully nothing will be printed in the
prompt, but if an error occurred it will be reported.  It should be
noted that the package file used for installation is not needed for
removal, and that only the package name as reported by `pkg list'
should be used when removing a package.  It is possible to remove
several packages at once by writing several package names after the
`pkg uninstall' command.

   To minimize the amount of code duplication between packages it is
possible that one package depends on another one.  If a package depends
on another, it will check if that package is installed during
installation.  If it is not, an error will be reported and the package
will not be installed.  This behavior can be disabled by passing the
`-nodeps' flag to the `pkg install' command

     pkg install -nodeps my_package_with_dependencies.tar.gz

Since the installed package expects its dependencies to be installed it
may not function correctly.  Because of this it is not recommended to
disable dependency checking.

 -- Command:  pkg COMMAND PKG_NAME
 -- Command:  pkg COMMAND OPTION PKG_NAME
     Manage packages (groups of add-on functions) for Octave.
     Different actions are available depending on the value of COMMAND.

     Available commands:

    `install'
          Install named packages.  For example,

               pkg install image-1.0.0.tar.gz

          installs the package found in the file `image-1.0.0.tar.gz'.

          The OPTION variable can contain options that affect the manner
          in which a package is installed.  These options can be one or
          more of

         `-nodeps'
               The package manager will disable dependency checking.
               With this option it is possible to install a package
               even when it depends on another package which is not
               installed on the system.  *Use this option with care.*

         `-noauto'
               The package manager will not automatically load the
               installed package when starting Octave.  This overrides
               any setting within the package.

         `-auto'
               The package manager will automatically load the
               installed package when starting Octave.  This overrides
               any setting within the package.

         `-local'
               A local installation (package available only to current
               user) is forced, even if the user has system privileges.

         `-global'
               A global installation (package available to all users)
               is forced, even if the user doesn't normally have system
               privileges.

         `-forge'
               Install a package directly from the Octave-Forge
               repository.  This requires an internet connection and
               the cURL library.

         `-verbose'
               The package manager will print the output of all
               commands as they are performed.

    `update'
          Check installed Octave-Forge packages against repository and
          update any outdated items.  This requires an internet
          connection and the cURL library.  Usage:

               pkg update

    `uninstall'
          Uninstall named packages.  For example,

               pkg uninstall image

          removes the `image' package from the system.  If another
          installed package depends on the `image' package an error
          will be issued.  The package can be uninstalled anyway by
          using the `-nodeps' option.

    `load'
          Add named packages to the path.  After loading a package it is
          possible to use the functions provided by the package.  For
          example,

               pkg load image

          adds the `image' package to the path.  It is possible to load
          all installed packages at once with the keyword `all'.  Usage:

               pkg load all

    `unload'
          Remove named packages from the path.  After unloading a
          package it is no longer possible to use the functions
          provided by the package.  It is possible to unload all
          installed packages at once with the keyword `all'.  Usage:

               pkg unload all

    `list'
          Show the list of currently installed packages.  For example,

               installed_packages = pkg ("list")

          returns a cell array containing a structure for each
          installed package.

          If two output arguments are requested `pkg' splits the list of
          installed packages into those which were installed by the
          current user, and those which were installed by the system
          administrator.

               [user_packages, system_packages] = pkg ("list")

          The option '-forge' lists packages available at the
          Octave-Forge repository.  This requires an internet
          connection and the cURL library.  For example:

               oct_forge_pkgs = pkg ("list", "-forge")

    `describe'
          Show a short description of the named installed packages,
          with the option '-verbose' also list functions provided by
          the package.  For example,

               pkg describe -verbose all

          will describe all installed packages and the functions they
          provide.  If one output is requested a cell of structure
          containing the description and list of functions of each
          package is returned as output rather than printed on screen:

               desc = pkg ("describe", "secs1d", "image")

          If any of the requested packages is not installed, pkg
          returns an error, unless a second output is requested:

               [desc, flag] = pkg ("describe", "secs1d", "image")

          FLAG will take one of the values "Not installed", "Loaded" or
          "Not loaded" for each of the named packages.

    `prefix'
          Set the installation prefix directory.  For example,

               pkg prefix ~/my_octave_packages

          sets the installation prefix to `~/my_octave_packages'.
          Packages will be installed in this directory.

          It is possible to get the current installation prefix by
          requesting an output argument.  For example:

               pfx = pkg ("prefix")

          The location in which to install the architecture dependent
          files can be independently specified with an addition
          argument.  For example:

               pkg prefix ~/my_octave_packages ~/my_arch_dep_pkgs

    `local_list'
          Set the file in which to look for information on locally
          installed packages.  Locally installed packages are those
          that are available only to the current user.  For example:

               pkg local_list ~/.octave_packages

          It is possible to get the current value of local_list with
          the following

               pkg local_list

    `global_list'
          Set the file in which to look for information on globally
          installed packages.  Globally installed packages are those
          that are available to all users.  For example:

               pkg global_list /usr/share/octave/octave_packages

          It is possible to get the current value of global_list with
          the following

               pkg global_list

    `build'
          Build a binary form of a package or packages.  The binary
          file produced will itself be an Octave package that can be
          installed normally with `pkg'.  The form of the command to
          build a binary package is

               pkg build builddir image-1.0.0.tar.gz ...

          where `builddir' is the name of a directory where the
          temporary installation will be produced and the binary
          packages will be found.  The options `-verbose' and `-nodeps'
          are respected, while all other options are ignored.

    `rebuild'
          Rebuild the package database from the installed directories.
          This can be used in cases where the package database has been
          corrupted.  It can also take the `-auto' and `-noauto'
          options to allow the autoloading state of a package to be
          changed.  For example,

               pkg rebuild -noauto image

          will remove the autoloading status of the image package.



File: octave.info,  Node: Using Packages,  Next: Administrating Packages,  Prev: Installing and Removing Packages,  Up: Packages

37.2 Using Packages
===================

By default installed packages are available from the Octave prompt, but
it is possible to control this using the `pkg load' and `pkg unload'
commands.  The functions from a package can be removed from the Octave
path by typing

     pkg unload package_name

where `package_name' is the name of the package to be removed from the
path.

   In much the same way a package can be added to the Octave path by
typing

     pkg load package_name


File: octave.info,  Node: Administrating Packages,  Next: Creating Packages,  Prev: Using Packages,  Up: Packages

37.3 Administrating Packages
============================

On UNIX-like systems it is possible to make both per-user and
system-wide installations of a package.  If the user performing the
installation is `root' the packages will be installed in a system-wide
directory that defaults to `OCTAVE_HOME/share/octave/packages/'.  If
the user is not `root' the default installation directory is
`~/octave/'.  Packages will be installed in a subdirectory of the
installation directory that will be named after the package.  It is
possible to change the installation directory by using the `pkg prefix'
command

     pkg prefix new_installation_directory

The current installation directory can be retrieved by typing

     current_installation_directory = pkg prefix

   To function properly the package manager needs to keep some
information about the installed packages.  For per-user packages this
information is by default stored in the file `~/.octave_packages' and
for system-wide installations it is stored in
`OCTAVE_HOME/share/octave/octave_packages'.  The path to the per-user
file can be changed with the `pkg local_list' command

     pkg local_list /path/to/new_file

For system-wide installations this can be changed in the same way using
the `pkg global_list' command.  If these commands are called without a
new path, the current path will be returned.


File: octave.info,  Node: Creating Packages,  Prev: Administrating Packages,  Up: Packages

37.4 Creating Packages
======================

Internally a package is simply a gzipped tar file that contains a top
level directory of any given name.  This directory will in the
following be referred to as `package' and may contain the following
files:


`package/COPYING'
     This is a required file containing the license of the package.  No
     restrictions is made on the license in general.  If however the
     package contains dynamically linked functions the license must be
     compatible with the GNU General Public License.

`package/DESCRIPTION'
     This is a required file containing information about the package.
     *Note The DESCRIPTION File::, for details on this file.

`package/ChangeLog'
     This is an optional file describing all the changes made to the
     package source files.

`package/INDEX'
     This is an optional file describing the functions provided by the
     package.  If this file is not given then one with be created
     automatically from the functions in the package and the
     `Categories' keyword in the `DESCRIPTION' file.  *Note The INDEX
     File::, for details on this file.

`package/NEWS'
     This is an optional file describing all user-visible changes worth
     mentioning.  As this file increases on size, old entries can be
     moved into `package/ONEWS'.

`package/ONEWS'
     This is an optional file describing old entries from the `NEWS'
     file.

`package/PKG_ADD'
     An optional file that includes commands that are run when the
     package is added to the users path.  Note that `PKG_ADD'
     directives in the source code of the package will also be added to
     this file by the Octave package manager.  Note that symbolic links
     are to be avoided in packages, as symbolic links do not exist on
     some file systems, and so a typical use for this file is the
     replacement of the symbolic link

          ln -s foo.oct bar.oct

     with an autoload directive like

          autoload ('bar', which ('foo'));

     *Note PKG_ADD and PKG_DEL Directives::, for details on `PKG_ADD'
     directives.

`package/PKG_DEL'
     An optional file that includes commands that are run when the
     package is removed from the users path.  Note that `PKG_DEL'
     directives in the source code of the package will also be added to
     this file by the Octave package manager.  *Note PKG_ADD and
     PKG_DEL Directives::, for details on `PKG_DEL' directives.

`package/pre_install.m'
     This is an optional script that is run prior to the installation
     of a package.

`package/post_install.m'
     This is an optional script that is run after the installation of a
     package.

`package/on_uninstall.m'
     This is an optional script that is run prior to the removal of a
     package.

   Besides the above mentioned files, a package can also contain on or
more of the following directories:


`package/inst'
     An optional directory containing any files that are directly
     installed by the package.  Typically this will include any
     `m'-files.

`package/src'
     An optional directory containing code that must be built prior to
     the packages installation.  The Octave package manager will execute
     `./configure' in this directory if this script exists, and will
     then call `make' if a file `Makefile' exists in this directory.
     `make install' will however not be called.  The environment
     variables `MKOCTFILE', `OCTAVE_CONFIG', and `OCTAVE' will be set
     to the full paths of the programs `mkoctfile', `octave-config',
     and `octave', respectively, of the correct version when
     `configure' and `make' are called.  If a file called `FILES'
     exists all files listed there will be copied to the `inst'
     directory, so they also will be installed.  If the `FILES' file
     doesn't exist, `src/*.m' and `src/*.oct' will be copied to the
     `inst' directory.

`package/doc'
     An optional directory containing documentation for the package.
     The files in this directory will be directly installed in a
     sub-directory of the installed package for future reference.

`package/bin'
     An optional directory containing files that will be added to the
     Octave `EXEC_PATH' when the package is loaded.  This might contain
     external scripts, etc., called by functions within the package.

* Menu:

* The DESCRIPTION File::
* The INDEX File::
* PKG_ADD and PKG_DEL Directives::


File: octave.info,  Node: The DESCRIPTION File,  Next: The INDEX File,  Up: Creating Packages

37.4.1 The DESCRIPTION File
---------------------------

The `DESCRIPTION' file contains various information about the package,
such as its name, author, and version.  This file has a very simple
format


   * Lines starting with `#' are comments.

   * Lines starting with a blank character are continuations from the
     previous line.

   * Everything else is of the form `NameOfOption: ValueOfOption'.

The following is a simple example of a `DESCRIPTION' file

     Name: The name of my package
     Version: 1.0.0
     Date: 2007-18-04
     Author: The name (and possibly email) of the package author.
     Maintainer: The name (and possibly email) of the current
      package maintainer.
     Title: The title of the package
     Description: A short description of the package.  If this
      description gets too long for one line it can continue
      on the next by adding a space to the beginning of the
      following lines.
     License: GPL version 3 or later

   The package manager currently recognizes the following keywords


`Name'
     Name of the package.

`Version'
     Version of the package.  A package version must be 3 numbers
     separated by a dot.

`Date'
     Date of last update.

`Author'
     Original author of the package.

`Maintainer'
     Maintainer of the package.

`Title'
     A one line description of the package.

`Description'
     A one paragraph description of the package.

`Categories'
     Optional keyword describing the package (if no `INDEX' file is
     given this is mandatory).

`Problems'
     Optional list of known problems.

`Url'
     Optional list of homepages related to the package.

`Autoload'
     Optional field that sets the default loading behavior for the
     package.  If set to `yes', `true' or `on', then Octave will
     automatically load the package when starting.  Otherwise the
     package must be manually loaded with the pkg load command.  This
     default behavior can be overridden when the package is installed.

`Depends'
     A list of other Octave packages that this package depends on.
     This can include dependencies on particular versions, with a format

          Depends: package (>= 1.0.0)

     Possible operators are `<', `<=', `==', `>=' or `>'.  If the part
     of the dependency in `()' is missing, any version of the package
     is acceptable.  Multiple dependencies can be defined either as a
     comma separated list or on separate `Depends' lines.

`License'
     An optional short description of the used license (e.g., GPL
     version 3 or newer).  This is optional since the file `COPYING' is
     mandatory.

`SystemRequirements'
     These are the external install dependencies of the package and are
     not checked by the package manager.  This is here as a hint to the
     distribution packager.  They follow the same conventions as the
     `Depends' keyword.

`BuildRequires'
     These are the external build dependencies of the package and are
     not checked by the package manager.  This is here as a hint to the
     distribution packager.  They follow the same conventions as the
     `Depends' keyword.  Note that in general, packaging systems such
     as `rpm' or `deb' and autoprobe the install dependencies from the
     build dependencies, and therefore the often a `BuildRequires'
     dependency removes the need for a `SystemRequirements' dependency.


The developer is free to add additional arguments to the `DESCRIPTION'
file for their own purposes.  One further detail to aid the packager is
that the `SystemRequirements' and `BuildRequires' keywords can have a
distribution dependent section, and the automatic build process will
use these.  An example of the format of this is

     BuildRequires: libtermcap-devel [Mandriva] libtermcap2-devel

where the first package name will be used as a default and if the RPMs
are built on a Mandriva distribution, then the second package name will
be used instead.


File: octave.info,  Node: The INDEX File,  Next: PKG_ADD and PKG_DEL Directives,  Prev: The DESCRIPTION File,  Up: Creating Packages

37.4.2 The INDEX File
---------------------

The optional `INDEX' file provides a categorical view of the functions
in the package.  This file has a very simple format


   * Lines beginning with `#' are comments.

   * The first non-comment line should look like this

          toolbox >> Toolbox name

   * Lines beginning with an alphabetical character indicates a new
     category of functions.

   * Lines starting with a white space character indicate that the
     function names on the line belong to the last mentioned category.

The format can be summarized with the following example.

     # A comment
     toolbox >> Toolbox name
     Category Name 1
      function1 function2 function3
      function4
     Category Name 2
      function2 function5

   If you wish to refer to a function that users might expect to find
in your package but is not there, providing a work around or pointing
out that the function is available elsewhere, you can use:

     fn = workaround description

This workaround description will not appear when listing functions in
the package with `pkg describe' but they will be published in the HTML
documentation online.  Workaround descriptions can use any HTML markup,
but keep in mind that it will be enclosed in a bold-italic environment.
For the special case of:

     fn = use <code>alternate expression</code>

the bold-italic is automatically suppressed.  You will need to use
`<code>' even in references:

     fn = use <a href="someothersite.html"><code>fn</code></a>

Sometimes functions are only partially compatible, in which case you
can list the non-compatible cases separately.  To refer to another
function in the package, use `<f>fn</f>'.  For example:

     eig (a, b) = use <f>qz</f>

Since sites may have many missing functions, you can define a macro
rather than typing the same link over and again.

     $id = expansion

defines the macro id.  You can use `$id' anywhere in the description
and it will be expanded.  For example:

     $TSA = see <a href="link_to_spctools">SPC Tools</a>
     arcov = $TSA <code>armcv</code>

id is any string of letters, numbers and `_'.


File: octave.info,  Node: PKG_ADD and PKG_DEL Directives,  Prev: The INDEX File,  Up: Creating Packages

37.4.3 PKG_ADD and PKG_DEL Directives
-------------------------------------

If the package contains files called `PKG_ADD' or `PKG_DEL' the
commands in these files will be executed when the package is added or
removed from the users path.  In some situations such files are a bit
cumbersome to maintain, so the package manager supports automatic
creation of such files.  If a source file in the package contains a
`PKG_ADD' or `PKG_DEL' directive they will be added to either the
`PKG_ADD' or `PKG_DEL' files.

   In `m'-files a `PKG_ADD' directive looks like this

     ## PKG_ADD: some_octave_command

Such lines should be added before the `function' keyword.  In C++ files
a `PKG_ADD' directive looks like this

     // PKG_ADD: some_octave_command

In both cases `some_octave_command' should be replaced by the command
that should be placed in the `PKG_ADD' file.  `PKG_DEL' directives work
in the same way, except the `PKG_ADD' keyword is replaced with
`PKG_DEL' and the commands get added to the `PKG_DEL' file.


File: octave.info,  Node: Dynamically Linked Functions,  Next: Test and Demo Functions,  Prev: Packages,  Up: Top

Appendix A Dynamically Linked Functions
***************************************

Octave has the possibility of including compiled code as dynamically
linked extensions and then using these extensions as if they were part
of Octave itself.  Octave can call C++ code through its native oct-file
interface or C code through its mex interface.  It can also indirectly
call functions written in any other language through a simple wrapper.
The reasons to write code in a compiled language might be either to
link to an existing piece of code and allow it to be used within
Octave, or to allow improved performance for key pieces of code.

   Before going further, you should first determine if you really need
to use dynamically linked functions at all.  Before proceeding with
writing any dynamically linked function to improve performance you
should address ask yourself

   * Can I get the same functionality using the Octave scripting
     language only?

   * Is it thoroughly optimized Octave code?  Vectorization of Octave
     code, doesn't just make it concise, it generally significantly
     improves its performance.  Above all, if loops must be used, make
     sure that the allocation of space for variables takes place
     outside the loops using an assignment to a matrix of the right
     size, or zeros.

   * Does it make as much use as possible of existing built-in library
     routines?  These are highly optimized and many do not carry the
     overhead of being interpreted.

   * Does writing a dynamically linked function represent useful
     investment of your time, relative to staying in Octave?

   Also, as oct- and mex-files are dynamically linked to Octave, they
introduce the possibility of Octave crashing due to errors in the user
code.  For example a segmentation violation in the user's code will
cause Octave to abort.

* Menu:

* Oct-Files::
* Mex-Files::
* Standalone Programs::


File: octave.info,  Node: Oct-Files,  Next: Mex-Files,  Up: Dynamically Linked Functions

A.1 Oct-Files
=============

* Menu:

* Getting Started with Oct-Files::
* Matrices and Arrays in Oct-Files::
* Character Strings in Oct-Files::
* Cell Arrays in Oct-Files::
* Structures in Oct-Files::
* Sparse Matrices in Oct-Files::
* Accessing Global Variables in Oct-Files::
* Calling Octave Functions from Oct-Files::
* Calling External Code from Oct-Files::
* Allocating Local Memory in Oct-Files::
* Input Parameter Checking in Oct-Files::
* Exception and Error Handling in Oct-Files::
* Documentation and Test of Oct-Files::


File: octave.info,  Node: Getting Started with Oct-Files,  Next: Matrices and Arrays in Oct-Files,  Up: Oct-Files

A.1.1 Getting Started with Oct-Files
------------------------------------

The basic command to build oct-files is `mkoctfile' and it can be call
from within octave or from the command line.

 -- Command:  mkoctfile [-options] file ...
 -- Function File: [OUTPUT, STATUS = mkoctfile (...)
     The `mkoctfile' function compiles source code written in C, C++,
     or Fortran.  Depending on the options used with `mkoctfile', the
     compiled code can be called within Octave or can be used as a
     stand-alone application.

     `mkoctfile' can be called from the shell prompt or from the Octave
     prompt.  Calling it from the Octave prompt simply delegates the
     call to the shell prompt.  The output is stored in the OUTPUT
     variable and the exit status in the STATUS variable.

     `mkoctfile' accepts the following options, all of which are
     optional except for the file name of the code you wish to compile:

    `-I DIR'
          Add the include directory DIR to compile commands.

    `-D DEF'
          Add the definition DEF to the compiler call.

    `-l LIB'
          Add the library LIB to the link command.

    `-L DIR'
          Add the library directory DIR to the link command.

    `-M'
    `--depend'
          Generate dependency files (.d) for C and C++ source files.

    `-R DIR'
          Add the run-time path to the link command.

    `-Wl,...'
          Pass flags though the linker like "-Wl,-rpath=...".  The
          quotes are needed since commas are interpreted as command
          separators.

    `-W...'
          Pass flags though the compiler like "-Wa,OPTION".

    `-c'
          Compile but do not link.

    `-g'
          Enable debugging options for compilers.

    `-o FILE'
    `--output FILE'
          Output file name.  Default extension is .oct (or .mex if
          `--mex' is specified) unless linking a stand-alone executable.

    `-p VAR'
    `--print VAR'
          Print the configuration variable VAR.  Recognized variables
          are:

                  ALL_CFLAGS                FFTW3F_LIBS
                  ALL_CXXFLAGS              FLIBS
                  ALL_FFLAGS                FPICFLAG
                  ALL_LDFLAGS               INCFLAGS
                  BLAS_LIBS                 LAPACK_LIBS
                  CC                        LDFLAGS
                  CFLAGS                    LD_CXX
                  CPICFLAG                  LD_STATIC_FLAG
                  CPPFLAGS                  LFLAGS
                  CXX                       LIBCRUFT
                  CXXFLAGS                  LIBOCTAVE
                  CXXPICFLAG                LIBOCTINTERP
                  DEPEND_EXTRA_SED_PATTERN  LIBS
                  DEPEND_FLAGS              OCTAVE_LIBS
                  DL_LD                     OCTAVE_LINK_DEPS
                  DL_LDFLAGS                OCT_LINK_DEPS
                  EXEEXT                    RDYNAMIC_FLAG
                  F77                       READLINE_LIBS
                  F77_INTEGER_8_FLAG        SED
                  FFLAGS                    XTRA_CFLAGS
                  FFTW3_LDFLAGS             XTRA_CXXFLAGS
                  FFTW3_LIBS
                  FFTW3F_LDFLAGS

    `--link-stand-alone'
          Link a stand-alone executable file.

    `--mex'
          Assume we are creating a MEX file.  Set the default output
          extension to ".mex".

    `-s'
    `--strip'
          Strip the output file.

    `-v'
    `--verbose'
          Echo commands as they are executed.

    `file'
          The file to compile or link.  Recognized file types are

                  .c    C source
                  .cc   C++ source
                  .C    C++ source
                  .cpp  C++ source
                  .f    Fortran source (fixed form)
                  .F    Fortran source (fixed form)
                  .f90  Fortran source (free form)
                  .F90  Fortran source (free form)
                  .o    object file
                  .a    library file


   Consider the short C++ example:

     #include <octave/oct.h>

     DEFUN_DLD (helloworld, args, nargout,
       "Hello World Help String")
     {
       int nargin = args.length ();
       octave_stdout << "Hello World has " << nargin
             << " input arguments and "
             << nargout << " output arguments.\n";
       return octave_value_list ();
     }

   This example although short introduces the basics of writing a C++
function that can be dynamically linked to Octave.  The easiest way to
make available most of the definitions that might be necessary for a C++
oct-file in Octave is to use the `#include <octave/oct.h>' header.
Note that `octave/oct.h' is a C++ header and cannot be directly
`#include''ed in a C source file, nor any other language.  What follows
is mostly C++, with a discussion of other languages in section *note
Calling External Code from Oct-Files::.

   The macro that defines the entry point into the dynamically loaded
function is `DEFUN_DLD'.  This macro takes four arguments, these being

  1. The function name as it will be seen in Octave,

  2. The list of arguments to the function of type `octave_value_list',

  3. The number of output arguments, which can and often is omitted if
     not used, and

  4. The string that will be seen as the help text of the function.

   The return type of functions defined with `DEFUN_DLD' is always
`octave_value_list'.

   There are a couple of important considerations in the choice of
function name.  Firstly, it must be a valid Octave function name and so
must be a sequence of letters, digits and underscores, not starting
with a digit.  Secondly, as Octave uses the function name to define the
filename it attempts to find the function in, the function name in the
`DEFUN_DLD' macro must match the filename of the oct-file.  Therefore,
the above function should be in a file `helloworld.cc', and it should be
compiled to an oct-file using the command

     mkoctfile helloworld.cc

   This will create a file called `helloworld.oct', that is the compiled
version of the function.  It should be noted that it is perfectly
acceptable to have more than one `DEFUN_DLD' function in a source file.
However, there must either be a symbolic link to the oct-file for each
of the functions defined in the source code with the `DEFUN_DLD' macro
or the autoload (*note Function Files::) function should be used.

   The rest of this function then shows how to find the number of input
arguments, how to print through the octave pager, and return from the
function.  After compiling this function as above, an example of its use
is

     helloworld (1, 2, 3)
     -| Hello World has 3 input arguments and 0 output arguments.


File: octave.info,  Node: Matrices and Arrays in Oct-Files,  Next: Character Strings in Oct-Files,  Prev: Getting Started with Oct-Files,  Up: Oct-Files

A.1.2 Matrices and Arrays in Oct-Files
--------------------------------------

Octave supports a number of different array and matrix classes, the
majority of which are based on the Array class.  The exception is the
sparse matrix types discussed separately below.  There are three basic
matrix types

`Matrix'
     A double precision matrix class defined in dMatrix.h,

`ComplexMatrix'
     A complex matrix class defined in CMatrix.h, and

`BoolMatrix'
     A boolean matrix class defined in boolMatrix.h.

   These are the basic two-dimensional matrix types of octave.  In
additional there are a number of multi-dimensional array types, these
being

`NDArray'
     A double precision array class defined in `dNDArray.h'

`ComplexNDarray'
     A complex array class defined in `CNDArray.h'

`boolNDArray'
     A boolean array class defined in `boolNDArray.h'

`int8NDArray'
`int16NDArray'
`int32NDArray'
`int64NDArray'
     8, 16, 32 and 64-bit signed array classes defined in
     `int8NDArray.h', `int16NDArray.h', etc.

`uint8NDArray'
`uint16NDArray'
`uint32NDArray'
`uint64NDArray'
     8, 16, 32 and 64-bit unsigned array classes defined in
     `uint8NDArray.h', `uint16NDArray.h', etc.

   There are several basic means of constructing matrices of
multi-dimensional arrays.  Considering the `Matrix' type as an example

   * We can create an empty matrix or array with the empty constructor.
     For example

          Matrix a;

     This can be used on all matrix and array types

   * Define the dimensions of the matrix or array with a dim_vector.
     For example

          dim_vector dv (2);
          dv(0) = 2; dv(1) = 2;
          Matrix a (dv);

     This can be used on all matrix and array types

   * Define the number of rows and columns in the matrix.  For example:

          Matrix a (2, 2)

     However, this constructor can only be used with the matrix types.

   These types all share a number of basic methods and operators, a
selection of which include

 -- Method: T& operator () (octave_idx_type)
 -- Method: T& elem (octave_idx_type)
     The `()' operator or `elem' method allow the values of the matrix
     or array to be read or set.  These can take a single argument,
     which is of type `octave_idx_type', that is the index into the
     matrix or array.  Additionally, the matrix type allows two
     argument versions of the `()' operator and elem method, giving the
     row and column index of the value to obtain or set.

   Note that these functions do significant error checking and so in
some circumstances the user might prefer to access the data of the
array or matrix directly through the fortran_vec method discussed below.

 -- Method: octave_idx_type nelem (void) const
     The total number of elements in the matrix or array.

 -- Method: size_t byte_size (void) const
     The number of bytes used to store the matrix or array.

 -- Method: dim_vector dims (void) const
     The dimensions of the matrix or array in value of type dim_vector.

 -- Method: void resize (const dim_vector&)
     A method taking either an argument of type `dim_vector', or in the
     case of a matrix two arguments of type `octave_idx_type' defining
     the number of rows and columns in the matrix.

 -- Method: T* fortran_vec (void)
     This method returns a pointer to the underlying data of the matrix
     or a array so that it can be manipulated directly, either within
     Octave or by an external library.

   Operators such an `+', `-', or `*' can be used on the majority of
the above types.  In addition there are a number of methods that are of
interest only for matrices such as `transpose', `hermitian', `solve',
etc.

   The typical way to extract a matrix or array from the input
arguments of `DEFUN_DLD' function is as follows

     #include <octave/oct.h>

     DEFUN_DLD (addtwomatrices, args, , "Add A to B")
     {
       int nargin = args.length ();
       if (nargin != 2)
         print_usage ();
       else
         {
           NDArray A = args(0).array_value ();
           NDArray B = args(1).array_value ();
           if (! error_state)
             return octave_value (A + B);
         }
       return octave_value_list ();
     }

   To avoid segmentation faults causing Octave to abort, this function
explicitly checks that there are sufficient arguments available before
accessing these arguments.  It then obtains two multi-dimensional arrays
of type `NDArray' and adds these together.  Note that the array_value
method is called without using the `is_matrix_type' type, and instead
the error_state is checked before returning `A + B'.  The reason to
prefer this is that the arguments might be a type that is not an
`NDArray', but it would make sense to convert it to one.  The
`array_value' method allows this conversion to be performed
transparently if possible, and sets `error_state' if it is not.

   `A + B', operating on two `NDArray''s returns an `NDArray', which is
cast to an `octave_value' on the return from the function.  An example
of the use of this demonstration function is

     addtwomatrices (ones (2, 2), ones (2, 2))
           =>  2  2
               2  2

   A list of the basic `Matrix' and `Array' types, the methods to
extract these from an `octave_value' and the associated header is
listed below.

`RowVector'            `row_vector_value'            `dRowVector.h'
`ComplexRowVector'     `complex_row_vector_value'    `CRowVector.h'
`ColumnVector'         `column_vector_value'         `dColVector.h'
`ComplexColumnVector'  `complex_column_vector_value' `CColVector.h'
`Matrix'               `matrix_value'                `dMatrix.h'
`ComplexMatrix'        `complex_matrix_value'        `CMatrix.h'
`boolMatrix'           `bool_matrix_value'           `boolMatrix.h'
`charMatrix'           `char_matrix_value'           `chMatrix.h'
`NDArray'              `array_value'                 `dNDArray.h'
`ComplexNDArray'       `complex_array_value'         `CNDArray.h'
`boolNDArray'          `bool_array_value'            `boolNDArray.h'
`charNDArray'          `char_array_value'            `charNDArray.h'
`int8NDArray'          `int8_array_value'            `int8NDArray.h'
`int16NDArray'         `int16_array_value'           `int16NDArray.h'
`int32NDArray'         `int32_array_value'           `int32NDArray.h'
`int64NDArray'         `int64_array_value'           `int64NDArray.h'
`uint8NDArray'         `uint8_array_value'           `uint8NDArray.h'
`uint16NDArray'        `uint16_array_value'          `uint16NDArray.h'
`uint32NDArray'        `uint32_array_value'          `uint32NDArray.h'
`uint64NDArray'        `uint64_array_value'          `uint64NDArray.h'


File: octave.info,  Node: Character Strings in Oct-Files,  Next: Cell Arrays in Oct-Files,  Prev: Matrices and Arrays in Oct-Files,  Up: Oct-Files

A.1.3 Character Strings in Oct-Files
------------------------------------

In Octave a character string is just a special `Array' class.  Consider
the example:

     #include <octave/oct.h>

     DEFUN_DLD (stringdemo, args, , "String Demo")
     {
       int nargin = args.length();
       octave_value_list retval;

       if (nargin != 1)
         print_usage ();
       else
         {
           charMatrix ch = args(0).char_matrix_value ();

           if (! error_state)
             {
               if (args(0).is_sq_string ())
                 retval(1) = octave_value (ch, true);
               else
                 retval(1) = octave_value (ch, true, '\'');

               octave_idx_type nr = ch.rows();
               for (octave_idx_type i = 0; i < nr / 2; i++)
                 {
                   std::string tmp = ch.row_as_string (i);
                   ch.insert (ch.row_as_string(nr-i-1).c_str(),
                              i, 0);
                   ch.insert (tmp.c_str(), nr-i-1, 0);
                 }
               retval(0) = octave_value (ch, true);
             }
         }
       return retval;
     }

   An example of the use of this function is

     s0 = ["First String"; "Second String"];
     [s1,s2] = stringdemo (s0)
     => s1 = Second String
             First String

     => s2 = First String
             Second String

     typeinfo (s2)
     => sq_string
     typeinfo (s1)
     => string

   One additional complication of strings in Octave is the difference
between single quoted and double quoted strings.  To find out if an
`octave_value' contains a single or double quoted string an example is

         if (args(0).is_sq_string ())
           octave_stdout <<
             "First argument is a singularly quoted string\n";
         else if (args(0).is_dq_string ())
           octave_stdout <<
             "First argument is a doubly quoted string\n";

   Note however, that both types of strings are represented by the
`charNDArray' type, and so when assigning to an `octave_value', the
type of string should be specified.  For example:

     octave_value_list retval;
     charNDArray c;
     ...
     // Create single quoted string
     retval(1) = octave_value (ch, true, '\'');

     // Create a double quoted string
     retval(0) = octave_value (ch, true);


File: octave.info,  Node: Cell Arrays in Oct-Files,  Next: Structures in Oct-Files,  Prev: Character Strings in Oct-Files,  Up: Oct-Files

A.1.4 Cell Arrays in Oct-Files
------------------------------

Octave's cell type is equally accessible within oct-files.  A cell
array is just an array of `octave_value's, and so each element of the
cell array can then be treated just like any other `octave_value'.  A
simple example is

     #include <octave/oct.h>
     #include <octave/Cell.h>

     DEFUN_DLD (celldemo, args, , "Cell Demo")
     {
       octave_value_list retval;
       int nargin = args.length ();

       if (nargin != 1)
         print_usage ();
       else
         {
           Cell c = args (0).cell_value ();
           if (! error_state)
             for (octave_idx_type i = 0; i < c.nelem (); i++)
               retval(i) = c.elem (i);
         }

       return retval;
     }

   Note that cell arrays are used less often in standard oct-files and
so the `Cell.h' header file must be explicitly included.  The rest of
this example extracts the `octave_value's one by one from the cell
array and returns be as individual return arguments.  For example
consider

     [b1, b2, b3] = celldemo ({1, [1, 2], "test"})
     =>
     b1 =  1
     b2 =

        1   2

     b3 = test


File: octave.info,  Node: Structures in Oct-Files,  Next: Sparse Matrices in Oct-Files,  Prev: Cell Arrays in Oct-Files,  Up: Oct-Files

A.1.5 Structures in Oct-Files
-----------------------------

A structure in Octave is map between a number of fields represented and
their values.  The Standard Template Library `map' class is used, with
the pair consisting of a `std::string' and an octave `Cell' variable.

   A simple example demonstrating the use of structures within
oct-files is

     #include <octave/oct.h>
     #include <octave/ov-struct.h>

     DEFUN_DLD (structdemo, args, , "Struct demo.")
     {
       int nargin = args.length ();
       octave_value retval;

       if (args.length () == 2)
         {
           octave_scalar_map arg0 = args(0).scalar_map_value ();

           if (! error_state)
             {
               std::string arg1 = args(1).string_value ();

               if (! error_state)
                 {
                   octave_value tmp = arg0.contents (arg1);

                   if (tmp.is_defined ())
                     {
                       octave_scalar_map st;

                       st.assign ("selected", tmp);

                       retval = octave_value (st);
                     }
                   else
                     error ("sruct does not contain field named '%s'\n",
                            arg1.c_str ());
                 }
               else
                 error ("expecting character string as second argument");
             }
           else
             error ("expecting struct as first argument");
         }
       else
         print_usage ();

       return retval;
     }

   An example of its use is

     x.a = 1; x.b = "test"; x.c = [1, 2];
     structdemo (x, "b")
     => selected = test

   The commented code above demonstrates how to iterate over all of the
fields of the structure, where as the following code demonstrates
finding a particular field in a more concise manner.

   As can be seen the `contents' method of the `Octave_map' class
returns a `Cell' which allows structure arrays to be represented.
Therefore, to obtain the underlying `octave_value' we write

     octave_value tmp = arg0.contents (p1) (0);

where the trailing (0) is the () operator on the `Cell' object.  We can
equally iterate of the elements of the Cell array to address the
elements of the structure array.


File: octave.info,  Node: Sparse Matrices in Oct-Files,  Next: Accessing Global Variables in Oct-Files,  Prev: Structures in Oct-Files,  Up: Oct-Files

A.1.6 Sparse Matrices in Oct-Files
----------------------------------

There are three classes of sparse objects that are of interest to the
user.

`SparseMatrix'
     A double precision sparse matrix class

`SparseComplexMatrix'
     A complex sparse matrix class

`SparseBoolMatrix'
     A boolean sparse matrix class

   All of these classes inherit from the `Sparse<T>' template class,
and so all have similar capabilities and usage.  The `Sparse<T>' class
was based on Octave `Array<T>' class, and so users familiar with
Octave's `Array' classes will be comfortable with the use of the sparse
classes.

   The sparse classes will not be entirely described in this section,
due to their similarity with the existing `Array' classes.  However,
there are a few differences due the different nature of sparse objects,
and these will be described.  Firstly, although it is fundamentally
possible to have N-dimensional sparse objects, the Octave sparse
classes do not allow them at this time.  So all operations of the
sparse classes must be 2-dimensional.  This means that in fact
`SparseMatrix' is similar to Octave's `Matrix' class rather than its
`NDArray' class.

* Menu:

* Array and Sparse Differences::
* Creating Sparse Matrices in Oct-Files::
* Using Sparse Matrices in Oct-Files::


File: octave.info,  Node: Array and Sparse Differences,  Next: Creating Sparse Matrices in Oct-Files,  Up: Sparse Matrices in Oct-Files

A.1.6.1 The Differences between the Array and Sparse Classes
............................................................

The number of elements in a sparse matrix is considered to be the number
of non-zero elements rather than the product of the dimensions.
Therefore

     SparseMatrix sm;
     ...
     int nel = sm.nelem ();

returns the number of non-zero elements.  If the user really requires
the number of elements in the matrix, including the non-zero elements,
they should use `numel' rather than `nelem'.  Note that for very large
matrices, where the product of the two dimensions is larger than the
representation of an unsigned int, then `numel' can overflow.  An
example is `speye(1e6)' which will create a matrix with a million rows
and columns, but only a million non-zero elements.  Therefore the
number of rows by the number of columns in this case is more than two
hundred times the maximum value that can be represented by an unsigned
int.  The use of `numel' should therefore be avoided useless it is known
it won't overflow.

   Extreme care must be take with the elem method and the "()" operator,
which perform basically the same function.  The reason is that if a
sparse object is non-const, then Octave will assume that a request for
a zero element in a sparse matrix is in fact a request to create this
element so it can be filled.  Therefore a piece of code like

     SparseMatrix sm;
     ...
     for (int j = 0; j < nc; j++)
       for (int i = 0; i < nr; i++)
         std::cerr << " (" << i << "," << j << "): " << sm(i,j)
                   << std::endl;

is a great way of turning the sparse matrix into a dense one, and a
very slow way at that since it reallocates the sparse object at each
zero element in the matrix.

   An easy way of preventing the above from happening is to create a
temporary constant version of the sparse matrix.  Note that only the
container for the sparse matrix will be copied, while the actual
representation of the data will be shared between the two versions of
the sparse matrix.  So this is not a costly operation.  For example,
the above would become

     SparseMatrix sm;
     ...
     const SparseMatrix tmp (sm);
     for (int j = 0; j < nc; j++)
       for (int i = 0; i < nr; i++)
         std::cerr << " (" << i << "," << j << "): " << tmp(i,j)
                   << std::endl;

   Finally, as the sparse types aren't just represented as a contiguous
block of memory, the `fortran_vec' method of the `Array<T>' is not
available.  It is however replaced by three separate methods `ridx',
`cidx' and `data', that access the raw compressed column format that
the Octave sparse matrices are stored in.  Additionally, these methods
can be used in a manner similar to `elem', to allow the matrix to be
accessed or filled.  However, in that case it is up to the user to
respect the sparse matrix compressed column format discussed previous.


File: octave.info,  Node: Creating Sparse Matrices in Oct-Files,  Next: Using Sparse Matrices in Oct-Files,  Prev: Array and Sparse Differences,  Up: Sparse Matrices in Oct-Files

A.1.6.2 Creating Sparse Matrices in Oct-Files
.............................................

You have several alternatives for creating a sparse matrix.  You can
first create the data as three vectors representing the row and column
indexes and the data, and from those create the matrix.  Or
alternatively, you can create a sparse matrix with the appropriate
amount of space and then fill in the values.  Both techniques have their
advantages and disadvantages.

   Here is an example of how to create a small sparse matrix with the
first technique

     int nz = 4, nr = 3, nc = 4;

     ColumnVector ridx (nz);
     ColumnVector cidx (nz);
     ColumnVector data (nz);

     ridx(0) = 0; ridx(1) = 0; ridx(2) = 1; ridx(3) = 2;
     cidx(0) = 0; cidx(1) = 1; cidx(2) = 3; cidx(3) = 3;
     data(0) = 1; data(1) = 2; data(2) = 3; data(3) = 4;

     SparseMatrix sm (data, ridx, cidx, nr, nc);

which creates the matrix given in section *note Storage of Sparse
Matrices::.  Note that the compressed matrix format is not used at the
time of the creation of the matrix itself, however it is used
internally.

   As previously mentioned, the values of the sparse matrix are stored
in increasing column-major ordering.  Although the data passed by the
user does not need to respect this requirement, the pre-sorting the
data significantly speeds up the creation of the sparse matrix.

   The disadvantage of this technique of creating a sparse matrix is
that there is a brief time where two copies of the data exists.
Therefore for extremely memory constrained problems this might not be
the right technique to create the sparse matrix.

   The alternative is to first create the sparse matrix with the desired
number of non-zero elements and then later fill those elements in.  The
easiest way to do this is

     int nz = 4, nr = 3, nc = 4;
     SparseMatrix sm (nr, nc, nz);
     sm(0,0) = 1; sm(0,1) = 2; sm(1,3) = 3; sm(2,3) = 4;

   That creates the same matrix as previously.  Again, although it is
not strictly necessary, it is significantly faster if the sparse matrix
is created in this manner that the elements are added in column-major
ordering.  The reason for this is that if the elements are inserted at
the end of the current list of known elements then no element in the
matrix needs to be moved to allow the new element to be inserted.  Only
the column indexes need to be updated.

   There are a few further points to note about this technique of
creating a sparse matrix.  Firstly, it is possible to create a sparse
matrix with fewer elements than are actually inserted in the matrix.
Therefore

     int nz = 4, nr = 3, nc = 4;
     SparseMatrix sm (nr, nc, 0);
     sm(0,0) = 1; sm(0,1) = 2; sm(1,3) = 3; sm(2,3) = 4;

is perfectly valid.  However it is a very bad idea.  The reason is that
as each new element is added to the sparse matrix the space allocated
to it is increased by reallocating the memory.  This is an expensive
operation, that will significantly slow this means of creating a sparse
matrix.  Furthermore, it is possible to create a sparse matrix with too
much storage, so having NZ above equaling 6 is also valid.  The
disadvantage is that the matrix occupies more memory than strictly
needed.

   It is not always easy to know the number of non-zero elements prior
to filling a matrix.  For this reason the additional storage for the
sparse matrix can be removed after its creation with the
"maybe_compress" function.  Furthermore, the maybe_compress can
deallocate the unused storage, but it can equally remove zero elements
from the matrix.  The removal of zero elements from the matrix is
controlled by setting the argument of the "maybe_compress" function to
be `true'.  However, the cost of removing the zeros is high because it
implies resorting the elements.  Therefore, if possible it is better is
the user doesn't add the zeros in the first place.  An example of the
use of "maybe_compress" is

       int nz = 6, nr = 3, nc = 4;

       SparseMatrix sm1 (nr, nc, nz);
       sm1(0,0) = 1; sm1(0,1) = 2; sm1(1,3) = 3; sm1(2,3) = 4;
       sm1.maybe_compress ();  // No zero elements were added

       SparseMatrix sm2 (nr, nc, nz);
       sm2(0,0) = 1; sm2(0,1) = 2; sm(0,2) = 0; sm(1,2) = 0;
       sm1(1,3) = 3; sm1(2,3) = 4;
       sm2.maybe_compress (true);  // Zero elements were added

   The use of the "maybe_compress" function should be avoided if
possible, as it will slow the creation of the matrices.

   A third means of creating a sparse matrix is to work directly with
the data in compressed row format.  An example of this technique might
be

     octave_value arg;
     ...
     int nz = 6, nr = 3, nc = 4;   // Assume we know the max no nz
     SparseMatrix sm (nr, nc, nz);
     Matrix m = arg.matrix_value ();

     int ii = 0;
     sm.cidx (0) = 0;
     for (int j = 1; j < nc; j++)
       {
         for (int i = 0; i < nr; i++)
           {
             double tmp = foo (m(i,j));
             if (tmp != 0.)
               {
                 sm.data(ii) = tmp;
                 sm.ridx(ii) = i;
                 ii++;
               }
           }
         sm.cidx(j+1) = ii;
      }
     sm.maybe_compress ();  // If don't know a-priori
                            // the final no of nz.

which is probably the most efficient means of creating the sparse
matrix.

   Finally, it might sometimes arise that the amount of storage
initially created is insufficient to completely store the sparse
matrix.  Therefore, the method `change_capacity' exists to reallocate
the sparse memory.  The above example would then be modified as

     octave_value arg;
     ...
     int nz = 6, nr = 3, nc = 4;   // Assume we know the max no nz
     SparseMatrix sm (nr, nc, nz);
     Matrix m = arg.matrix_value ();

     int ii = 0;
     sm.cidx (0) = 0;
     for (int j = 1; j < nc; j++)
       {
         for (int i = 0; i < nr; i++)
           {
             double tmp = foo (m(i,j));
             if (tmp != 0.)
               {
                 if (ii == nz)
                   {
                     nz += 2;   // Add 2 more elements
                     sm.change_capacity (nz);
                   }
                 sm.data(ii) = tmp;
                 sm.ridx(ii) = i;
                 ii++;
               }
           }
         sm.cidx(j+1) = ii;
      }
     sm.maybe_mutate ();  // If don't know a-priori
                          // the final no of nz.

   Note that both increasing and decreasing the number of non-zero
elements in a sparse matrix is expensive, as it involves memory
reallocation.  Also as parts of the matrix, though not its entirety,
exist as the old and new copy at the same time, additional memory is
needed.  Therefore if possible this should be avoided.


File: octave.info,  Node: Using Sparse Matrices in Oct-Files,  Prev: Creating Sparse Matrices in Oct-Files,  Up: Sparse Matrices in Oct-Files

A.1.6.3 Using Sparse Matrices in Oct-Files
..........................................

Most of the same operators and functions on sparse matrices that are
available from the Octave are equally available with oct-files.  The
basic means of extracting a sparse matrix from an `octave_value' and
returning them as an `octave_value', can be seen in the following
example.

     octave_value_list retval;

     SparseMatrix sm = args(0).sparse_matrix_value ();
     SparseComplexMatrix scm =
         args(1).sparse_complex_matrix_value ();
     SparseBoolMatrix sbm = args(2).sparse_bool_matrix_value ();
     ...
     retval(2) = sbm;
     retval(1) = scm;
     retval(0) = sm;

   The conversion to an octave-value is handled by the sparse
`octave_value' constructors, and so no special care is needed.


File: octave.info,  Node: Accessing Global Variables in Oct-Files,  Next: Calling Octave Functions from Oct-Files,  Prev: Sparse Matrices in Oct-Files,  Up: Oct-Files

A.1.7 Accessing Global Variables in Oct-Files
---------------------------------------------

Global variables allow variables in the global scope to be accessed.
Global variables can easily be accessed with oct-files using the
support functions `get_global_value' and `set_global_value'.
`get_global_value' takes two arguments, the first is a string
representing the variable name to obtain.  The second argument is a
boolean argument specifying what to do in the case that no global
variable of the desired name is found.  An example of the use of these
two functions is

     #include <octave/oct.h>

     DEFUN_DLD (globaldemo, args, , "Global demo.")
     {
       int nargin = args.length ();
       octave_value retval;

       if (nargin != 1)
         print_usage ();
       else
         {
           std::string s = args(0).string_value ();
           if (! error_state)
             {
               octave_value tmp = get_global_value (s, true);
               if (tmp.is_defined ())
                 retval = tmp;
               else
                 retval = "Global variable not found";

               set_global_value ("a", 42.0);
             }
         }
       return retval;
     }

   An example of its use is

     global a b
     b = 10;
     globaldemo ("b")
     => 10
     globaldemo ("c")
     => "Global variable not found"
     num2str (a)
     => 42


File: octave.info,  Node: Calling Octave Functions from Oct-Files,  Next: Calling External Code from Oct-Files,  Prev: Accessing Global Variables in Oct-Files,  Up: Oct-Files

A.1.8 Calling Octave Functions from Oct-Files
---------------------------------------------

There is often a need to be able to call another octave function from
within an oct-file, and there are many examples of such within octave
itself.  For example the `quad' function is an oct-file that calculates
the definite integral by quadrature over a user supplied function.

   There are also many ways in which a function might be passed.  It
might be passed as one of

  1. Function Handle

  2. Anonymous Function Handle

  3. Inline Function

  4. String

   The example below demonstrates an example that accepts all four
means of passing a function to an oct-file.

     #include <octave/oct.h>
     #include <octave/parse.h>

     DEFUN_DLD (funcdemo, args, nargout, "Function Demo")
     {
       int nargin = args.length();
       octave_value_list retval;

       if (nargin < 2)
         print_usage ();
       else
         {
           octave_value_list newargs;
           for (octave_idx_type i = nargin - 1; i > 0; i--)
             newargs (i - 1) = args(i);
           if (args(0).is_function_handle ()
               || args(0).is_inline_function ())
             {
               octave_function *fcn = args(0).function_value ();
               if (! error_state)
                 retval = feval (fcn, newargs, nargout);
             }
           else if (args(0).is_string ())
             {
               std::string fcn = args (0).string_value ();
               if (! error_state)
                 retval = feval (fcn, newargs, nargout);
             }
           else
             error ("funcdemo: expected string,",
                    " inline or function handle");
         }
       return retval;
     }

   The first argument to this demonstration is the user supplied
function and the following arguments are all passed to the user
function.

     funcdemo (@sin,1)
     => 0.84147
     funcdemo (@(x) sin(x), 1)
     => 0.84147
     funcdemo (inline ("sin(x)"), 1)
     => 0.84147
     funcdemo ("sin",1)
     => 0.84147
     funcdemo (@atan2, 1, 1)
     => 0.78540

   When the user function is passed as a string, the treatment of the
function is different.  In some cases it is necessary to always have the
user supplied function as an `octave_function' object.  In that case
the string argument can be used to create a temporary function like

     std::octave fcn_name = unique_symbol_name ("__fcn__");
     std::string fname = "function y = ";
     fname.append (fcn_name);
     fname.append ("(x) y = ");
     fcn = extract_function (args(0), "funcdemo", fcn_name,
                             fname, "; endfunction");
     ...
     if (fcn_name.length ())
       clear_function (fcn_name);

   There are two important things to know in this case.  The number of
input arguments to the user function is fixed, and in the above is a
single argument, and secondly to avoid leaving the temporary function
in the Octave symbol table it should be cleared after use.


File: octave.info,  Node: Calling External Code from Oct-Files,  Next: Allocating Local Memory in Oct-Files,  Prev: Calling Octave Functions from Oct-Files,  Up: Oct-Files

A.1.9 Calling External Code from Oct-Files
------------------------------------------

Linking external C code to Octave is relatively simple, as the C
functions can easily be called directly from C++.  One possible issue is
the declarations of the external C functions might need to be explicitly
defined as C functions to the compiler.  If the declarations of the
external C functions are in the header `foo.h', then the manner in
which to ensure that the C++ compiler treats these declarations as C
code is

     #ifdef __cplusplus
     extern "C"
     {
     #endif
     #include "foo.h"
     #ifdef __cplusplus
     }  /* end extern "C" */
     #endif

   Calling Fortran code however can pose some difficulties.  This is
due to differences in the manner in compilers treat the linking of
Fortran code with C or C++ code.  Octave supplies a number of macros
that allow consistent behavior across a number of compilers.

   The underlying Fortran code should use the `XSTOPX' function to
replace the Fortran `STOP' function.  `XSTOPX' uses the Octave
exception handler to treat failing cases in the Fortran code
explicitly.  Note that Octave supplies its own replacement BLAS
`XERBLA' function, which uses `XSTOPX'.

   If the underlying code calls `XSTOPX', then the `F77_XFCN' macro
should be used to call the underlying Fortran function.  The Fortran
exception state can then be checked with the global variable
`f77_exception_encountered'.  If `XSTOPX' will not be called, then the
`F77_FCN' macro should be used instead to call the Fortran code.

   There is no harm in using `F77_XFCN' in all cases, except that for
Fortran code that is short running and executes a large number of times,
there is potentially an overhead in doing so.  However, if `F77_FCN' is
used with code that calls `XSTOP', Octave can generate a segmentation
fault.

   An example of the inclusion of a Fortran function in an oct-file is
given in the following example, where the C++ wrapper is

     #include <octave/oct.h>
     #include <octave/f77-fcn.h>

     extern "C"
     {
       F77_RET_T
       F77_FUNC (fortsub, FORTSUB)
             (const int&, double*, F77_CHAR_ARG_DECL
              F77_CHAR_ARG_LEN_DECL);
     }

     DEFUN_DLD (fortdemo , args , , "Fortran Demo.")
     {
       octave_value_list retval;
       int nargin = args.length();
       if (nargin != 1)
         print_usage ();
       else
         {
           NDArray a = args(0).array_value ();
           if (! error_state)
             {
               double *av = a.fortran_vec ();
               octave_idx_type na = a.nelem ();
               OCTAVE_LOCAL_BUFFER (char, ctmp, 128);

               F77_XFCN (fortsub, FORTSUB, (na, av, ctmp
                         F77_CHAR_ARG_LEN (128)));

               retval(1) = std::string (ctmp);
               retval(0) = a;
             }
         }
       return retval;
     }

and the Fortran function is

           subroutine fortsub (n, a, s)
           implicit none
           character*(*) s
           real*8 a(*)
           integer*4 i, n, ioerr
           do i = 1, n
             if (a(i) .eq. 0d0) then
               call xstopx ('fortsub: divide by zero')
             else
               a(i) = 1d0 / a(i)
             endif
           enddo
           write (unit = s, fmt = '(a,i3,a,a)', iostat = ioerr)
          $       'There are ', n,
          $       ' values in the input vector', char(0)
           if (ioerr .ne. 0) then
             call xstopx ('fortsub: error writing string')
           endif
           return
           end

   This example demonstrates most of the features needed to link to an
external Fortran function, including passing arrays and strings, as well
as exception handling.  An example of the behavior of this function is

     [b, s] = fortdemo (1:3)
     =>
       b = 1.00000   0.50000   0.33333
       s = There are   3 values in the input vector
     [b, s] = fortdemo(0:3)
     error: fortsub:divide by zero
     error: exception encountered in Fortran subroutine fortsub_
     error: fortdemo: error in Fortran


File: octave.info,  Node: Allocating Local Memory in Oct-Files,  Next: Input Parameter Checking in Oct-Files,  Prev: Calling External Code from Oct-Files,  Up: Oct-Files

A.1.10 Allocating Local Memory in Oct-Files
-------------------------------------------

Allocating memory within an oct-file might seem easy as the C++
new/delete operators can be used.  However, in that case care must be
taken to avoid memory leaks.  The preferred manner in which to allocate
memory for use locally is to use the `OCTAVE_LOCAL_BUFFER' macro.  An
example of its use is

     OCTAVE_LOCAL_BUFFER (double, tmp, len)

that returns a pointer `tmp' of type `double *' of length `len'.


File: octave.info,  Node: Input Parameter Checking in Oct-Files,  Next: Exception and Error Handling in Oct-Files,  Prev: Allocating Local Memory in Oct-Files,  Up: Oct-Files

A.1.11 Input Parameter Checking in Oct-Files
--------------------------------------------

As oct-files are compiled functions they have the possibility of causing
Octave to abort abnormally.  It is therefore important that each and
every function has the minimum of parameter checking needed to ensure
that Octave behaves well.

   The minimum requirement, as previously discussed, is to check the
number of input arguments before using them to avoid referencing a non
existent argument.  However, it some case this might not be sufficient
as the underlying code imposes further constraints.  For example an
external function call might be undefined if the input arguments are not
integers, or if one of the arguments is zero.  Therefore, oct-files
often need additional input parameter checking.

   There are several functions within Octave that might be useful for
the purposes of parameter checking.  These include the methods of the
octave_value class like `is_real_matrix', etc., but equally include
more specialized functions.  Some of the more common ones are
demonstrated in the following example.

     #include <octave/oct.h>

     DEFUN_DLD (paramdemo, args, nargout,
                "Parameter Check Demo.")
     {
       int nargin = args.length ();
       octave_value retval;

       if (nargin != 1)
         print_usage();
       else if (nargout != 0)
         error ("paramdemo: function has no output arguments");
       else
         {
           NDArray m = args(0).array_value();
           double min_val = -10.0;
           double max_val = 10.0;
           octave_stdout << "Properties of input array:\n";
           if (m.any_element_is_negative ())
             octave_stdout << "  includes negative values\n";
           if (m.any_element_is_inf_or_nan())
             octave_stdout << "  includes Inf or NaN values\n";
           if (m.any_element_not_one_or_zero())
             octave_stdout <<
               "  includes other values than 1 and 0\n";
           if (m.all_elements_are_int_or_inf_or_nan())
             octave_stdout <<
               "  includes only int, Inf or NaN values\n";
           if (m.all_integers (min_val, max_val))
             octave_stdout <<
               "  includes only integers in [-10,10]\n";
         }
       return retval;
     }

An example of its use is:

     paramdemo ([1, 2, NaN, Inf])
     => Properties of input array:
           includes Inf or NaN values
           includes other values than 1 and 0
           includes only int, Inf or NaN values


File: octave.info,  Node: Exception and Error Handling in Oct-Files,  Next: Documentation and Test of Oct-Files,  Prev: Input Parameter Checking in Oct-Files,  Up: Oct-Files

A.1.12 Exception and Error Handling in Oct-Files
------------------------------------------------

Another important feature of Octave is its ability to react to the user
typing `Control-C' even during calculations.  This ability is based on
the C++ exception handler, where memory allocated by the C++ new/delete
methods are automatically released when the exception is treated.  When
writing an oct-file, to allow Octave to treat the user typing
`Control-C', the `OCTAVE_QUIT' macro is supplied.  For example:

     for (octave_idx_type i = 0; i < a.nelem (); i++)
       {
         OCTAVE_QUIT;
         b.elem(i) = 2. * a.elem(i);
       }

   The presence of the `OCTAVE_QUIT' macro in the inner loop allows
Octave to treat the user request with the `Control-C'.  Without this
macro, the user must either wait for the function to return before the
interrupt is processed, or press `Control-C' three times to force
Octave to exit.

   The `OCTAVE_QUIT' macro does impose a very small speed penalty, and
so for loops that are known to be small it might not make sense to
include `OCTAVE_QUIT'.

   When creating an oct-file that uses an external libraries, the
function might spend a significant portion of its time in the external
library.  It is not generally possible to use the `OCTAVE_QUIT' macro
in this case.  The alternative in this case is

     BEGIN_INTERRUPT_IMMEDIATELY_IN_FOREIGN_CODE;
     ...  some code that calls a "foreign" function ...
     END_INTERRUPT_IMMEDIATELY_IN_FOREIGN_CODE;

   The disadvantage of this is that if the foreign code allocates any
memory internally, then this memory might be lost during an interrupt,
without being deallocated.  Therefore, ideally Octave itself should
allocate any memory that is needed by the foreign code, with either the
fortran_vec method or the `OCTAVE_LOCAL_BUFFER' macro.

   The Octave unwind_protect mechanism (*note The `unwind_protect'
Statement::) can also be used in oct-files.  In conjunction with the
exception handling of Octave, it is important to enforce that certain
code is run to allow variables, etc. to be restored even if an
exception occurs.  An example of the use of this mechanism is

     #include <octave/oct.h>
     #include <octave/unwind-prot.h>

     void
     err_hand (const char *fmt, ...)
     {
       // Do nothing!!
     }

     DEFUN_DLD (unwinddemo, args, nargout, "Unwind Demo")
     {
       int nargin = args.length();
       octave_value retval;
       if (nargin < 2)
         print_usage ();
       else
         {
           NDArray a = args(0).array_value ();
           NDArray b = args(1).array_value ();

           if (! error_state)
             {
               unwind_protect::begin_frame ("Funwinddemo");
               unwind_protect_ptr (current_liboctave_warning_handler);
               set_liboctave_warning_handler(err_hand);
               retval = octave_value (quotient (a, b));
               unwind_protect::run_frame ("Funwinddemo");
             }
         }
       return retval;
     }

   As can be seen in the example:

     unwinddemo (1, 0)
     => Inf
     1 / 0
     => warning: division by zero
        Inf

   The division by zero (and in fact all warnings) is disabled in the
`unwinddemo' function.


File: octave.info,  Node: Documentation and Test of Oct-Files,  Prev: Exception and Error Handling in Oct-Files,  Up: Oct-Files

A.1.13 Documentation and Test of Oct-Files
------------------------------------------

The documentation of an oct-file is the fourth string parameter of the
`DEFUN_DLD' macro.  This string can be formatted in the same manner as
the help strings for user functions (*note Documentation Tips::),
however there are some issue that are particular to the formatting of
help strings within oct-files.

   The major issue is that the help string will typically be longer
than a single line of text, and so the formatting of long help strings
need to be taken into account.  There are several manners in which to
treat this issue, but the most common is illustrated in the following
example,

     DEFUN_DLD (do_what_i_want, args, nargout,
       "-*- texinfo -*-\n\
     @deftypefn {Function File} {} do_what_i_say (@var{n})\n\
     A function that does what the user actually wants rather\n\
     than what they requested.\n\
     @end deftypefn")
     {
     ...
     }

where, as can be seen, end line of text within the help string is
terminated by `\n\' which is an embedded new-line in the string
together with a C++ string continuation character.  Note that the final
`\' must be the last character on the line.

   Octave also includes the ability to embed the test and demonstration
code for a function within the code itself (*note Test and Demo
Functions::).  This can be used from within oct-files (or in fact any
file) with certain provisos.  Firstly, the test and demo functions of
Octave look for a `%!' as the first characters on a new-line to
identify test and demonstration code.  This is equally a requirement for
oct-files.  Furthermore the test and demonstration code must be included
in a comment block of the compiled code to avoid it being interpreted by
the compiler.  Finally, the Octave test and demonstration code must have
access to the source code of the oct-file and not just the compiled code
as the tests are stripped from the compiled code.  An example in an
oct-file might be

     /*

     %!error (sin())
     %!error (sin(1,1))
     %!assert (sin([1,2]),[sin(1),sin(2)])

     */


File: octave.info,  Node: Mex-Files,  Next: Standalone Programs,  Prev: Oct-Files,  Up: Dynamically Linked Functions

A.2 Mex-Files
=============

Octave includes an interface to allow legacy mex-files to be compiled
and used with Octave.  This interface can also be used to share code
between Octave and MATLAB users.  However, as mex-files expose the
MATLAB's internal API, and the internal structure of Octave is
different, a mex-file can never have the same performance in Octave as
the equivalent oct-file.  In particular to support the manner in which
mex-files access the variables passed to mex functions, there are a
significant number of additional copies of memory when calling or
returning from a mex function.  For this reason, new code should be
written using the oct-file interface discussed above if possible.

* Menu:

* Getting Started with Mex-Files::
* Working with Matrices and Arrays in Mex-Files::
* Character Strings in Mex-Files::
* Cell Arrays with Mex-Files::
* Structures with Mex-Files::
* Sparse Matrices with Mex-Files::
* Calling Other Functions in Mex-Files::


File: octave.info,  Node: Getting Started with Mex-Files,  Next: Working with Matrices and Arrays in Mex-Files,  Up: Mex-Files

A.2.1 Getting Started with Mex-Files
------------------------------------

The basic command to build a mex-file is either `mkoctfile --mex' or
`mex'.  The first can either be used from within Octave or from the
command line.  However, to avoid issues with MATLAB's own `mex'
command, the use of the command `mex' is limited to within Octave.

 -- Function File:  mex [options] file ...
     Compile source code written in C, C++, or Fortran, to a MEX file.
     This is equivalent to `mkoctfile --mex [options] file'.

     *See also:* *note mkoctfile: doc-mkoctfile.

 -- Function File:  mexext ()
     Return the filename extension used for MEX files.

     *See also:* *note mex: doc-mex.

   One important difference with the use of `mex' between MATLAB and
Octave is that the header file "matrix.h" is implicitly included through
the inclusion of "mex.h".  This is to avoid a conflict with the Octave
file "Matrix.h" with operating systems and compilers that don't
distinguish between filenames in upper and lower case

   Consider the short example:

     #include "mex.h"

     void
     mexFunction (int nlhs, mxArray *plhs[], int nrhs,
                  const mxArray *prhs[])
     {
       mxArray *v = mxCreateDoubleMatrix (1, 1, mxREAL);
       double *data = mxGetPr (v);
       *data = 1.23456789;
       plhs[0] = v;
     }

   This simple example demonstrates the basics of writing a mex-file.
The entry point into the mex-file is defined by `mexFunction'.  Note
that the function name is not explicitly included in the `mexFunction'
and so there can only be a single `mexFunction' entry point per-file.
Also the name of the function is determined by the name of the mex-file
itself.  Therefore if the above function is in the file
`firstmexdemo.c', it can be compiled with

     mkoctfile --mex firstmexdemo.c

which creates a file `firstmexdemo.mex'.  The function can then be run
from Octave as

     firstmexdemo()
     => 1.2346

   It should be noted that the mex-file contains no help string for the
functions it contains.  To document mex-files, there should exist an
m-file in the same directory as the mex-file itself.  Taking the above
as an example, we would therefore have a file `firstmexdemo.m' that
might contain the text

     %FIRSTMEXDEMO Simple test of the functionality of a mex-file.

   In this case, the function that will be executed within Octave will
be given by the mex-file, while the help string will come from the
m-file.  This can also be useful to allow a sample implementation of the
mex-file within the Octave language itself for testing purposes.

   Although we cannot have multiple entry points into a single mex-file,
we can use the `mexFunctionName' function to determine what name the
mex-file was called with.  This can be used to alter the behavior of
the mex-file based on the function name.  For example if

     #include "mex.h"

     void
     mexFunction (int nlhs, mxArray *plhs[], int nrhs,
                  const mxArray *prhs[])
     {
       const char *nm;
       nm = mexFunctionName ();
       mexPrintf ("You called function: %s\n", nm);
       if (strcmp (nm, "myfunc") == 0)
         mexPrintf ("This is the principal function\n", nm);
       return;
     }

is in file `myfunc.c', and it is compiled with

     mkoctfile --mex myfunc.c
     ln -s myfunc.mex myfunc2.mex

   Then as can be seen by

     myfunc()
     => You called function: myfunc
         This is the principal function
     myfunc2()
     => You called function: myfunc2

the behavior of the mex-file can be altered depending on the functions
name.

   Allow the user should only include `mex.h' in their code, Octave
declares additional functions, typedefs, etc., available to the user to
write mex-files in the headers `mexproto.h' and `mxarray.h'.


File: octave.info,  Node: Working with Matrices and Arrays in Mex-Files,  Next: Character Strings in Mex-Files,  Prev: Getting Started with Mex-Files,  Up: Mex-Files

A.2.2 Working with Matrices and Arrays in Mex-Files
---------------------------------------------------

The basic mex type of all variables is `mxArray'.  All variables, such
as matrices, cell arrays or structures are all stored in this basic
type, and this type serves basically the same purpose as the
octave_value class in oct-files.  That is it acts as a container for the
more specialized types.

   The `mxArray' structure contains at a minimum, the variable it
represents name, its dimensions, its type and whether the variable is
real or complex.  It can however contain a number of additional fields
depending on the type of the `mxArray'.  There are a number of
functions to create `mxArray' structures, including
`mxCreateCellArray', `mxCreateSparse' and the generic
`mxCreateNumericArray'.

   The basic functions to access the data contained in an array is
`mxGetPr'.  As the mex interface assumes that the real and imaginary
parts of a complex array are stored separately, there is an equivalent
function `mxGetPi' that get the imaginary part.  Both of these
functions are for use only with double precision matrices.  There also
exists the generic function `mxGetData' and `mxGetImagData' that
perform the same operation on all matrix types.  For example:

     mxArray *m;
     mwSize *dims;
     UINT32_T *pr;

     dims = (mwSize *) mxMalloc (2 * sizeof(mwSize));
     dims[0] = 2;
     dims[1] = 2;
     m = mxCreateNumericArray (2, dims, mxUINT32_CLASS, mxREAL);
     pr =  = (UINT32_T *) mxGetData (m);

   There are also the functions `mxSetPr', etc., that perform the
inverse, and set the data of an Array to use the block of memory pointed
to by the argument of `mxSetPr'.

   Note the type `mwSize' used above, and `mwIndex' are defined as the
native precision of the indexing in Octave on the platform on which the
mex-file is built.  This allows both 32- and 64-bit platforms to
support mex-files.  `mwSize' is used to define array dimension and
maximum number or elements, while `mwIndex' is used to define indexing
into arrays.

   An example that demonstration how to work with arbitrary real or
complex double precision arrays is given by the file `mypow2.c' as given
below.

     #include "mex.h"

     void
     mexFunction (int nlhs, mxArray* plhs[], int nrhs,
                  const mxArray* prhs[])
     {
       mwIndex i;
       mwSize n;
       double *vri, *vro;

       if (nrhs != 1 || ! mxIsNumeric (prhs[0]))
         mexErrMsgTxt ("expects matrix");

       n = mxGetNumberOfElements (prhs[0]);
       plhs[0] = (mxArray *) mxCreateNumericArray
         (mxGetNumberOfDimensions (prhs[0]),
          mxGetDimensions (prhs[0]), mxGetClassID (prhs[0]),
          mxIsComplex (prhs[0]));
       vri = mxGetPr (prhs[0]);
       vro = mxGetPr (plhs[0]);

       if (mxIsComplex (prhs[0]))
         {
           double *vii, *vio;
           vii = mxGetPi (prhs[0]);
           vio = mxGetPi (plhs[0]);

           for (i = 0; i < n; i++)
             {
               vro [i] = vri [i] * vri [i] - vii [i] * vii [i];
               vio [i] = 2 * vri [i] * vii [i];
             }
         }
       else
         {
           for (i = 0; i < n; i++)
             vro [i] = vri [i] * vri [i];
         }
     }

with an example of its use

     b = randn(4,1) + 1i * randn(4,1);
     all(b.^2 == mypow2(b))
     => 1

   The example above uses the functions `mxGetDimensions',
`mxGetNumberOfElements', and `mxGetNumberOfDimensions' to work with the
dimensions of multi-dimensional arrays.  The functions `mxGetM', and
`mxGetN' are also available to find the number of rows and columns in a
matrix.


File: octave.info,  Node: Character Strings in Mex-Files,  Next: Cell Arrays with Mex-Files,  Prev: Working with Matrices and Arrays in Mex-Files,  Up: Mex-Files

A.2.3 Character Strings in Mex-Files
------------------------------------

As mex-files do not make the distinction between single and double
quoted strings within Octave, there is perhaps less complexity in the
use of strings and character matrices in mex-files.  An example of their
use, that parallels the demo in `stringdemo.cc', is given in the file
`mystring.c', as seen below.

     #include <string.h>
     #include "mex.h"

     void
     mexFunction (int nlhs, mxArray *plhs[], int nrhs,
                  const mxArray *prhs[])
     {
       mwIndex i, j;
       mwSize m, n;
       mxChar *pi, *po;

       if (nrhs != 1 || ! mxIsChar (prhs[0]) ||
           mxGetNumberOfDimensions (prhs[0]) > 2)
         mexErrMsgTxt ("expecting char matrix");

       m = mxGetM (prhs[0]);
       n = mxGetN (prhs[0]);
       pi = mxGetChars (prhs[0]);
       plhs[0] = mxCreateNumericMatrix (m, n, mxCHAR_CLASS,
                                        mxREAL);
       po = mxGetChars (plhs[0]);

       for (j = 0; j < n; j++)
         for (i = 0; i < m; i++)
           po [j*m + m - 1 - i] = pi [j*m + i];
     }

An example of its expected output is

     mystring(["First String"; "Second String"])
     => s1 = Second String
             First String

   Other functions in the mex interface for handling character strings
are `mxCreateString', `mxArrayToString', and
`mxCreateCharMatrixFromStrings'.  In a mex-file, a character string is
considered to be a vector rather than a matrix.  This is perhaps an
arbitrary distinction as the data in the mxArray for the matrix is
consecutive in any case.


File: octave.info,  Node: Cell Arrays with Mex-Files,  Next: Structures with Mex-Files,  Prev: Character Strings in Mex-Files,  Up: Mex-Files

A.2.4 Cell Arrays with Mex-Files
--------------------------------

We can perform exactly the same operations in Cell arrays in mex-files
as we can in oct-files.  An example that reduplicates the functional of
the `celldemo.cc' oct-file in a mex-file is given by `mycell.c' as below

     #include "mex.h"

     void
     mexFunction (int nlhs, mxArray* plhs[], int nrhs,
                  const mxArray* prhs[])
     {
       mwSize n;
       mwIndex i;

       if (nrhs != 1 || ! mxIsCell (prhs[0]))
         mexErrMsgTxt ("expects cell");

       n = mxGetNumberOfElements (prhs[0]);
       n = (n > nlhs ? nlhs : n);

       for (i = 0; i < n; i++)
         plhs[i] = mxDuplicateArray (mxGetCell (prhs[0], i));
     }

which as can be seen below has exactly the same behavior as the oct-file
version.

     [b1, b2, b3] = mycell ({1, [1, 2], "test"})
     =>
     b1 =  1
     b2 =

        1   2

     b3 = test

   Note in the example the use of the `mxDuplicateArray' function.  This
is needed as the `mxArray' pointer returned by `mxGetCell' might be
deallocated.  The inverse function to `mxGetCell' is `mcSetCell' and is
defined as

     void mxSetCell (mxArray *ptr, int idx, mxArray *val);

   Finally, to create a cell array or matrix, the appropriate functions
are

     mxArray *mxCreateCellArray (int ndims, const int *dims);
     mxArray *mxCreateCellMatrix (int m, int n);


File: octave.info,  Node: Structures with Mex-Files,  Next: Sparse Matrices with Mex-Files,  Prev: Cell Arrays with Mex-Files,  Up: Mex-Files

A.2.5 Structures with Mex-Files
-------------------------------

The basic function to create a structure in a mex-file is
`mxCreateStructMatrix', which creates a structure array with a two
dimensional matrix, or `mxCreateStructArray'.

     mxArray *mxCreateStructArray (int ndims, int *dims,
                                   int num_keys,
                                   const char **keys);
     mxArray *mxCreateStructMatrix (int rows, int cols,
                                    int num_keys,
                                    const char **keys);

   Accessing the fields of the structure can then be performed with the
`mxGetField' and `mxSetField' or alternatively with the
`mxGetFieldByNumber' and `mxSetFieldByNumber' functions.

     mxArray *mxGetField (const mxArray *ptr, mwIndex index,
                          const char *key);
     mxArray *mxGetFieldByNumber (const mxArray *ptr,
                                  mwIndex index, int key_num);
     void mxSetField (mxArray *ptr, mwIndex index,
                      const char *key, mxArray *val);
     void mxSetFieldByNumber (mxArray *ptr, mwIndex index,
                              int key_num, mxArray *val);

   A difference between the oct-file interface to structures and the
mex-file version is that the functions to operate on structures in
mex-files directly include an `index' over the elements of the arrays
of elements per `field'.  Whereas the oct-file structure includes a
Cell Array per field of the structure.

   An example that demonstrates the use of structures in mex-file can be
found in the file `mystruct.c', as seen below

     #include "mex.h"

     void
     mexFunction (int nlhs, mxArray* plhs[], int nrhs,
                  const mxArray* prhs[])
     {
       int i;
       mwIndex j;
       mxArray *v;
       const char *keys[] = { "this", "that" };

       if (nrhs != 1 || ! mxIsStruct (prhs[0]))
         mexErrMsgTxt ("expects struct");

       for (i = 0; i < mxGetNumberOfFields (prhs[0]); i++)
         for (j = 0; j < mxGetNumberOfElements (prhs[0]); j++)
           {
             mexPrintf ("field %s(%d) = ",
                        mxGetFieldNameByNumber (prhs[0], i), j);
             v = mxGetFieldByNumber (prhs[0], j, i);
             mexCallMATLAB (0, 0, 1, &v, "disp");
           }

       v = mxCreateStructMatrix (2, 2, 2, keys);

       mxSetFieldByNumber (v, 0, 0, mxCreateString ("this1"));
       mxSetFieldByNumber (v, 0, 1, mxCreateString ("that1"));
       mxSetFieldByNumber (v, 1, 0, mxCreateString ("this2"));
       mxSetFieldByNumber (v, 1, 1, mxCreateString ("that2"));
       mxSetFieldByNumber (v, 2, 0, mxCreateString ("this3"));
       mxSetFieldByNumber (v, 2, 1, mxCreateString ("that3"));
       mxSetFieldByNumber (v, 3, 0, mxCreateString ("this4"));
       mxSetFieldByNumber (v, 3, 1, mxCreateString ("that4"));

       if (nlhs)
         plhs[0] = v;
     }

   An example of the behavior of this function within Octave is then

     a(1).f1 = "f11"; a(1).f2 = "f12";
     a(2).f1 = "f21"; a(2).f2 = "f22";
     b = mystruct(a)
     => field f1(0) = f11
         field f1(1) = f21
         field f2(0) = f12
         field f2(1) = f22
         b =
         {
           this =

           (,
             [1] = this1
             [2] = this2
             [3] = this3
             [4] = this4
           ,)

           that =

           (,
             [1] = that1
             [2] = that2
             [3] = that3
             [4] = that4
           ,)

         }


File: octave.info,  Node: Sparse Matrices with Mex-Files,  Next: Calling Other Functions in Mex-Files,  Prev: Structures with Mex-Files,  Up: Mex-Files

A.2.6 Sparse Matrices with Mex-Files
------------------------------------

The Octave format for sparse matrices is identical to the mex format in
that it is a compressed column sparse format.  Also in both, sparse
matrices are required to be two-dimensional.  The only difference is
that the real and imaginary parts of the matrix are stored separately.

   The mex-file interface, as well as using `mxGetM', `mxGetN',
`mxSetM', `mxSetN', `mxGetPr', `mxGetPi', `mxSetPr' and `mxSetPi', the
mex-file interface supplies the functions

     mwIndex *mxGetIr (const mxArray *ptr);
     mwIndex *mxGetJc (const mxArray *ptr);
     mwSize mxGetNzmax (const mxArray *ptr);

     void mxSetIr (mxArray *ptr, mwIndex *ir);
     void mxSetJc (mxArray *ptr, mwIndex *jc);
     void mxSetNzmax (mxArray *ptr, mwSize nzmax);

`mxGetNzmax' gets the maximum number of elements that can be stored in
the sparse matrix.  This is not necessarily the number of non-zero
elements in the sparse matrix.  `mxGetJc' returns an array with one
additional value than the number of columns in the sparse matrix.  The
difference between consecutive values of the array returned by
`mxGetJc' define the number of non-zero elements in each column of the
sparse matrix.  Therefore

     mwSize nz, n;
     mwIndex *Jc;
     mxArray *m;
     ...
     n = mxGetN (m);
     Jc = mxGetJc (m);
     nz = Jc[n];

returns the actual number of non-zero elements stored in the matrix in
`nz'.  As the arrays returned by `mxGetPr' and `mxGetPi' only contain
the non-zero values of the matrix, we also need a pointer to the rows
of the non-zero elements, and this is given by `mxGetIr'.  A complete
example of the use of sparse matrices in mex-files is given by the file
`mysparse.c' as seen below

     #include "mex.h"

     void
     mexFunction (int nlhs, mxArray *plhs[], int nrhs,
                  const mxArray *prhs[])
     {
       mwSize n, m, nz;
       mxArray *v;
       mwIndex i;
       double *pr, *pi;
       double *pr2, *pi2;
       mwIndex *ir, *jc;
       mwIndex *ir2, *jc2;

       if (nrhs != 1 || ! mxIsSparse (prhs[0]))
         mexErrMsgTxt ("expects sparse matrix");

       m = mxGetM (prhs [0]);
       n = mxGetN (prhs [0]);
       nz = mxGetNzmax (prhs [0]);

       if (mxIsComplex (prhs[0]))
         {
           mexPrintf ("Matrix is %d-by-%d complex",
                      " sparse matrix", m, n);
           mexPrintf (" with %d elements\n", nz);

           pr = mxGetPr (prhs[0]);
           pi = mxGetPi (prhs[0]);
           ir = mxGetIr (prhs[0]);
           jc = mxGetJc (prhs[0]);

           i = n;
           while (jc[i] == jc[i-1] && i != 0) i--;
           mexPrintf ("last non-zero element (%d, %d) =",
                      ir[nz-1]+ 1, i);
           mexPrintf (" (%g, %g)\n", pr[nz-1], pi[nz-1]);

           v = mxCreateSparse (m, n, nz, mxCOMPLEX);
           pr2 = mxGetPr (v);
           pi2 = mxGetPi (v);
           ir2 = mxGetIr (v);
           jc2 = mxGetJc (v);

           for (i = 0; i < nz; i++)
             {
               pr2[i] = 2 * pr[i];
               pi2[i] = 2 * pi[i];
               ir2[i] = ir[i];
             }
           for (i = 0; i < n + 1; i++)
             jc2[i] = jc[i];

           if (nlhs > 0)
             plhs[0] = v;
         }
       else if (mxIsLogical (prhs[0]))
         {
           bool *pbr, *pbr2;
           mexPrintf ("Matrix is %d-by-%d logical",
                      " sparse matrix", m, n);
           mexPrintf (" with %d elements\n", nz);

           pbr = mxGetLogicals (prhs[0]);
           ir = mxGetIr (prhs[0]);
           jc = mxGetJc (prhs[0]);

           i = n;
           while (jc[i] == jc[i-1] && i != 0) i--;
           mexPrintf ("last non-zero element (%d, %d) = %d\n",
                      ir[nz-1]+ 1, i, pbr[nz-1]);

           v = mxCreateSparseLogicalMatrix (m, n, nz);
           pbr2 = mxGetLogicals (v);
           ir2 = mxGetIr (v);
           jc2 = mxGetJc (v);

           for (i = 0; i < nz; i++)
             {
               pbr2[i] = pbr[i];
               ir2[i] = ir[i];
             }
           for (i = 0; i < n + 1; i++)
             jc2[i] = jc[i];

           if (nlhs > 0)
             plhs[0] = v;
         }
       else
         {
           mexPrintf ("Matrix is %d-by-%d real",
                      " sparse matrix", m, n);
           mexPrintf (" with %d elements\n", nz);

           pr = mxGetPr (prhs[0]);
           ir = mxGetIr (prhs[0]);
           jc = mxGetJc (prhs[0]);

           i = n;
           while (jc[i] == jc[i-1] && i != 0) i--;
           mexPrintf ("last non-zero element (%d, %d) = %g\n",
                     ir[nz-1]+ 1, i, pr[nz-1]);

           v = mxCreateSparse (m, n, nz, mxREAL);
           pr2 = mxGetPr (v);
           ir2 = mxGetIr (v);
           jc2 = mxGetJc (v);

           for (i = 0; i < nz; i++)
             {
               pr2[i] = 2 * pr[i];
               ir2[i] = ir[i];
             }
           for (i = 0; i < n + 1; i++)
             jc2[i] = jc[i];

           if (nlhs > 0)
             plhs[0] = v;
         }
     }


File: octave.info,  Node: Calling Other Functions in Mex-Files,  Prev: Sparse Matrices with Mex-Files,  Up: Mex-Files

A.2.7 Calling Other Functions in Mex-Files
------------------------------------------

It is also possible call other Octave functions from within a mex-file
using `mexCallMATLAB'.  An example of the use of `mexCallMATLAB' can be
see in the example below

     #include "mex.h"

     void
     mexFunction (int nlhs, mxArray* plhs[], int nrhs,
                  const mxArray* prhs[])
     {
       char *str;

       mexPrintf ("Hello, World!\n");

       mexPrintf ("I have %d inputs and %d outputs\n", nrhs,
                  nlhs);

       if (nrhs < 1 || ! mxIsString (prhs[0]))
         mexErrMsgTxt ("function name expected");

       str = mxArrayToString (prhs[0]);

       mexPrintf ("I'm going to call the function %s\n", str);

       mexCallMATLAB (nlhs, plhs, nrhs-1, prhs+1, str);

       mxFree (str);
     }

   If this code is in the file `myfeval.c', and is compiled to
`myfeval.mex', then an example of its use is

     myfeval("sin", 1)
     a = myfeval("sin", 1)
     => Hello, World!
         I have 2 inputs and 1 outputs
         I'm going to call the interpreter function sin
         a =  0.84147

   Note that it is not possible to use function handles or inline
functions within a mex-file.


File: octave.info,  Node: Standalone Programs,  Prev: Mex-Files,  Up: Dynamically Linked Functions

A.3 Standalone Programs
=======================

The libraries Octave itself uses, can be utilized in standalone
applications.  These applications then have access, for example, to the
array and matrix classes as well as to all the Octave algorithms.  The
following C++ program, uses class Matrix from `liboctave.a' or
`liboctave.so'.

     #include <iostream>
     #include <octave/oct.h>

     int
     main (void)
     {
       std::cout << "Hello Octave world!\n";
       int n = 2;
       Matrix a_matrix = Matrix (n, n);
       for (octave_idx_type i = 0; i < n; i++)
         {
           for (octave_idx_type j = 0; j < n; j++)
             {
               a_matrix (i, j) = (i + 1) * 10 + (j + 1);
             }
         }
       std::cout << a_matrix;
       return 0;
     }

mkoctfile can then be used to build a standalone application with a
command like

     $ mkoctfile --link-stand-alone standalone.cc -o standalone
     $ ./standalone
     Hello Octave world!
       11 12
       21 22
     $

   Note that the application `hello' will be dynamically linked against
the octave libraries and any octave support libraries.  The above
allows the Octave math libraries to be used by an application.  It does
not however allow the script files, oct-files or builtin functions of
Octave to be used by the application.  To do that the Octave interpreter
needs to be initialized first.  An example of how to do this can then be
seen in the code

     #include <iostream>
     #include <octave/oct.h>
     #include <octave/octave.h>
     #include <octave/parse.h>

     int
     main (void)
     {
       string_vector argv (2);
       argv(0) = "embedded";
       argv(1) = "-q";

       octave_main (2, argv.c_str_vec(), 1);

       octave_idx_type n = 2;
       Matrix a_matrix = Matrix (1, 2);

       std::cout << "GCD of [";
       for (octave_idx_type i = 0; i < n; i++)
         {
           a_matrix (i) = 5 * (i + 1);
           if (i != 0)
             std::cout << ", " << 5 * (i + 2);
           else
             std::cout << 5 * (i + 2);
         }
       std::cout << "] is ";

       octave_value_list in = octave_value (a_matrix);
       octave_value_list out = feval ("gcd", in, 1);

       if (!error_state && out.length () > 0)
         {
           a_matrix = out(0).matrix_value ();
           if (a_matrix.numel () == 1)
             std::cout << a_matrix(0) << "\n";
           else
             std::cout << "invalid\n";
         }
       else
         std::cout << "invalid\n";

       return 0;
     }

which is compiled and run as before as a standalone application with

     $ mkoctfile --link-stand-alone embedded.cc -o embedded
     $ ./embedded
     GCD of [10, 15] is 5
     $


File: octave.info,  Node: Test and Demo Functions,  Next: Tips and Standards,  Prev: Dynamically Linked Functions,  Up: Top

Appendix B Test and Demo Functions
**********************************

Octave includes a number of functions to allow the integration of
testing and demonstration code in the source code of the functions
themselves.

* Menu:

* Test Functions::
* Demonstration Functions::


File: octave.info,  Node: Test Functions,  Next: Demonstration Functions,  Up: Test and Demo Functions

B.1 Test Functions
==================

 -- Command:  test NAME
 -- Command:  test NAME quiet|normal|verbose
 -- Function File:  test ('NAME', 'quiet|normal|verbose', FID)
 -- Function File:  test ([], 'explain', FID)
 -- Function File: SUCCESS = test (...)
 -- Function File: [N, MAX] = test (...)
 -- Function File: [CODE, IDX] = test ('NAME', 'grabdemo')
     Perform tests from the first file in the loadpath matching NAME.
     `test' can be called as a command or as a function.  Called with a
     single argument NAME, the tests are run interactively and stop
     after the first error is encountered.

     With a second argument the tests which are performed and the
     amount of output is selected.

    'quiet'
          Don't report all the tests as they happen, just the errors.

    'normal'
          Report all tests as they happen, but don't do tests which
          require user interaction.

    'verbose'
          Do tests which require user interaction.

     The argument FID can be used to allow batch processing.  Errors
     can be written to the already open file defined by FID, and
     hopefully when Octave crashes this file will tell you what was
     happening when it did.  You can use `stdout' if you want to see
     the results as they happen.  You can also give a file name rather
     than an FID, in which case the contents of the file will be
     replaced with the log from the current test.

     Called with a single output argument SUCCESS, `test' returns true
     if all of the tests were successful.  Called with two output
     arguments N and MAX, the number of successful tests and the total
     number of tests in the file NAME are returned.

     If the second argument is the string 'grabdemo', the contents of
     the demo blocks are extracted but not executed.  Code for all code
     blocks is concatenated and returned as CODE with IDX being a
     vector of positions of the ends of the demo blocks.

     If the second argument is 'explain', then NAME is ignored and an
     explanation of the line markers used is written to the file FID.

     *See also:* *note assert: doc-assert, *note fail: doc-fail, *note
     error: doc-error, *note demo: doc-demo, *note example: doc-example.

   `test' scans the named script file looking for lines which start
with the identifier `%!'.  The prefix is stripped off and the rest of
the line is processed through the Octave interpreter.  If the code
generates an error, then the test is said to fail.

   Since `eval()' will stop at the first error it encounters, you must
divide your tests up into blocks, with anything in a separate block
evaluated separately.  Blocks are introduced by the keyword `test'
immediately following `%!'.  For example:

     %!test error ("this test fails!");
     %!test "test doesn't fail. it doesn't generate an error";

   When a test fails, you will see something like:

       ***** test error ("this test fails!")
     !!!!! test failed
     this test fails!

   Generally, to test if something works, you want to assert that it
produces a correct value.  A real test might look something like

     %!test
     %! A = [1, 2, 3; 4, 5, 6]; B = [1; 2];
     %! expect = [ A ; 2*A ];
     %! get = kron (B, A);
     %! if (any (size (expect) != size (get)))
     %!   error ("wrong size: expected %d,%d but got %d,%d",
     %!          size(expect), size(get));
     %! elseif (any (any (expect != get)))
     %!   error ("didn't get what was expected.");
     %! endif

   To make the process easier, use the `assert' function.  For example,
with `assert' the previous test is reduced to:

     %!test
     %! A = [1, 2, 3; 4, 5, 6]; B = [1; 2];
     %! assert (kron (B, A), [ A; 2*A ]);

   `assert' can accept a tolerance so that you can compare results
absolutely or relatively.  For example, the following all succeed:

     %!test assert (1+eps, 1, 2*eps)          # absolute error
     %!test assert (100+100*eps, 100, -2*eps) # relative error

   You can also do the comparison yourself, but still have assert
generate the error:

     %!test assert (isempty ([]))
     %!test assert ([1, 2; 3, 4] > 0)

   Because `assert' is so frequently used alone in a test block, there
is a shorthand form:

     %!assert (...)

which is equivalent to:

     %!test assert (...)

   Occasionally a block of tests will depend on having optional
functionality in Octave.  Before testing such blocks the availability of
the required functionality must be checked.  A `%!testif HAVE_XXX'
block will only be run if Octave was compiled with functionality
`HAVE_XXX'.  For example, the sparse single value decomposition,
`svds()', depends on having the ARPACK library.  All of the tests for
`svds' begin with

     %!testif HAVE_ARPACK

Review `config.h' or `octave_config_info ("DEFS")' to see some of the
possible values to check.

   Sometimes during development there is a test that should work but is
known to fail.  You still want to leave the test in because when the
final code is ready the test should pass, but you may not be able to
fix it immediately.  To avoid unnecessary bug reports for these known
failures, mark the block with `xtest' rather than `test':

     %!xtest assert (1==0)
     %!xtest fail ("success=1", "error")

In this case, the test will run and any failure will be reported.
However, testing is not aborted and subsequent test blocks will be
processed normally.  Another use of `xtest' is for statistical tests
which should pass most of the time but are known to fail occasionally.

   Each block is evaluated in its own function environment, which means
that variables defined in one block are not automatically shared with
other blocks.  If you do want to share variables, then you must declare
them as `shared' before you use them.  For example, the following
declares the variable A, gives it an initial value (default is empty),
and then uses it in several subsequent tests.

     %!shared A
     %! A = [1, 2, 3; 4, 5, 6];
     %!assert (kron ([1; 2], A), [ A; 2*A ]);
     %!assert (kron ([1, 2], A), [ A, 2*A ]);
     %!assert (kron ([1,2; 3,4], A), [ A,2*A; 3*A,4*A ]);

   You can share several variables at the same time:

     %!shared A, B

   You can also share test functions:

     %!function A = fn (B)
     %!  A = 2*B;
     %!endfunction
     %!assert (fn(2), 4);

   Note that all previous variables and values are lost when a new
shared block is declared.

   Error and warning blocks are like test blocks, but they only succeed
if the code generates an error.  You can check the text of the error is
correct using an optional regular expression `<pattern>'.  For example:

     %!error <passes!> error ("this test passes!");

   If the code doesn't generate an error, the test fails.  For example:

     %!error "this is an error because it succeeds.";

produces

       ***** error "this is an error because it succeeds.";
     !!!!! test failed: no error

   It is important to automate the tests as much as possible, however
some tests require user interaction.  These can be isolated into demo
blocks, which if you are in batch mode, are only run when called with
`demo' or the `verbose' option to `test'.  The code is displayed before
it is executed.  For example,

     %!demo
     %! T = [0:0.01:2*pi]; X = sin (T);
     %! plot (T, X);
     %! # you should now see a sine wave in your figure window

produces

     funcname example 1:
      T = [0:0.01:2*pi]; X = sin (T);
      plot (T, X);
      # you should now see a sine wave in your figure window

     Press <enter> to continue:

   Note that demo blocks cannot use any shared variables.  This is so
that they can be executed by themselves, ignoring all other tests.

   If you want to temporarily disable a test block, put `#' in place of
the block type.  This creates a comment block which is echoed in the
log file but not executed.  For example:

     %!#demo
     %! T = [0:0.01:2*pi]; X = sin (T);
     %! plot (T, X);
     %! # you should now see a sine wave in your figure window

Block type summary:
...................

`%!test'
     check that entire block is correct

`%!testif HAVE_XXX'
     check block only if Octave was compiled with feature HAVE_XXX.

`%!xtest'
     check block, report a test failure but do not abort testing.

`%!error'
     check for correct error message

`%!warning'
     check for correct warning message

`%!demo'
     demo only executes in interactive mode

`%!#'
     comment: ignore everything within the block

`%!shared x,y,z'
     declare variables for use in multiple tests

`%!function'
     define a function for use in multiple tests

`%!endfunction'
     close a function definition

`%!assert (x, y, tol)'
     shorthand for `%!test assert (x, y, tol)'

   You can also create test scripts for builtins and your own C++
functions.  To do so put a file with the bare function name (no .m
extension) in a directory in the load path and it will be discovered by
the `test' function.  Alternatively, you can embed tests directly in
your C++ code:

     /*
     %!test disp ("this is a test")
     */

or

     #if 0
     %!test disp ("this is a test")
     #endif

However, in this case the raw source code will need to be on the load
path and the user will have to remember to type `test ("funcname.cc")'.

 -- Function File:  assert (COND)
 -- Function File:  assert (COND, ERRMSG, ...)
 -- Function File:  assert (COND, MSG_ID, ERRMSG, ...)
 -- Function File:  assert (OBSERVED, EXPECTED)
 -- Function File:  assert (OBSERVED, EXPECTED, TOL)
     Produce an error if the specified condition is not met.  `assert'
     can be called in three different ways.

    `assert (COND)'
    `assert (COND, ERRMSG, ...)'
    `assert (COND, MSG_ID, ERRMSG, ...)'
          Called with a single argument COND, `assert' produces an
          error if COND is zero.  When called with more than one
          argument the additional arguments are passed to the `error'
          function.

    `assert (OBSERVED, EXPECTED)'
          Produce an error if observed is not the same as expected.
          Note that OBSERVED and EXPECTED can be scalars, vectors,
          matrices, strings, cell arrays, or structures.

    `assert (OBSERVED, EXPECTED, TOL)'
          Produce an error if observed is not the same as expected but
          equality comparison for numeric data uses a tolerance TOL.
          If TOL is positive then it is an absolute tolerance which
          will produce an error if `abs(OBSERVED - EXPECTED) >
          abs(TOL)'.  If TOL is negative then it is a relative
          tolerance which will produce an error if `abs(OBSERVED -
          EXPECTED) > abs(TOL * EXPECTED)'.  If EXPECTED is zero TOL
          will always be interpreted as an absolute tolerance.

     *See also:* *note test: doc-test, *note fail: doc-fail, *note
     error: doc-error.

 -- Function File:  fail (CODE)
 -- Function File:  fail (CODE, PATTERN)
 -- Function File:  fail (CODE, 'warning', PATTERN)
     Return true if CODE fails with an error message matching PATTERN,
     otherwise produce an error.  Note that CODE is a string and if
     CODE runs successfully, the error produced is:

                    expected error but got none

     If the code fails with a different error, the message produced is:

                    expected <pattern>
                    but got <text of actual error>

     The angle brackets are not part of the output.

     Called with three arguments, the behavior is similar to
     `fail(CODE, PATTERN)', but produces an error if no warning is
     given during code execution or if the code fails.

     *See also:* *note assert: doc-assert.


File: octave.info,  Node: Demonstration Functions,  Prev: Test Functions,  Up: Test and Demo Functions

B.2 Demonstration Functions
===========================

 -- Command:  demo NAME
 -- Command:  demo NAME N
 -- Function File:  demo ('NAME')
 -- Function File:  demo ('NAME', N)
     Run example code block N associated with the function NAME.  If N
     is not specified, all examples are run.

     Examples are stored in the script file, or in a file with the same
     name but no extension located on Octave's load path.  To keep
     examples separate from regular script code, all lines are prefixed
     by `%!'.  Each example must also be introduced by the keyword
     'demo' flush left to the prefix with no intervening spaces.  The
     remainder of the example can contain arbitrary Octave code.  For
     example:

          !demo
          ! t=0:0.01:2*pi; x = sin (t);
          ! plot (t,x)
          ! %-------------------------------------------------
          ! % the figure window shows one cycle of a sine wave

     Note that the code is displayed before it is executed, so a simple
     comment at the end suffices for labeling what is being shown.  It
     is generally not necessary to use `disp' or `printf' within the
     demo.

     Demos are run in a function environment with no access to external
     variables.  This means that every demo must have separate
     initialization code.  Alternatively, all demos can be combined
     into a single large demo with the code

          ! input("Press <enter> to continue: ","s");

     between the sections, but this is discouraged.  Other techniques
     to avoid multiple initialization blocks include using multiple
     plots with a new `figure' command between each plot, or using
     `subplot' to put multiple plots in the same window.

     Also, because demo evaluates within a function context, you cannot
     define new functions inside a demo.  If you must have function
     blocks, rather than just anonymous functions or inline functions,
     you will have to use `eval(example('function',n))' to see them.
     Because eval only evaluates one line, or one statement if the
     statement crosses multiple lines, you must wrap your demo in "if 1
     <demo stuff> endif" with the 'if' on the same line as 'demo'.  For
     example:

          !demo if 1
          !  function y=f(x)
          !    y=x;
          !  endfunction
          !  f(3)
          ! endif

     *See also:* *note test: doc-test, *note example: doc-example.

 -- Command:  example NAME
 -- Command:  example NAME N
 -- Function File:  example ('NAME')
 -- Function File:  example ('NAME', N)
 -- Function File: [S, IDX] = example (...)
     Display the code for example N associated with the function
     'NAME', but do not run it.  If N is not specified, all examples
     are displayed.

     When called with output arguments, the examples are returned in
     the form of a string S, with IDX indicating the ending position of
     the various examples.

     See `demo' for a complete explanation.

     *See also:* *note demo: doc-demo, *note test: doc-test.

 -- Function File:  rundemos ()
 -- Function File:  rundemos (DIRECTORY)
     Execute built-in demos for all function files in the specified
     directory.  If no directory is specified, operate on all
     directories in Octave's search path for functions.

     *See also:* *note runtests: doc-runtests, *note path: doc-path.

 -- Function File:  runtests ()
 -- Function File:  runtests (DIRECTORY)
     Execute built-in tests for all function files in the specified
     directory.  If no directory is specified, operate on all
     directories in Octave's search path for functions.

     *See also:* *note rundemos: doc-rundemos, *note path: doc-path.

 -- Function File:  speed (F, INIT, MAX_N, F2, TOL)
 -- Function File: [ORDER, N, T_F, T_F2] = speed (...)
     Determine the execution time of an expression (F) for various input
     values (N).  The N are log-spaced from 1 to MAX_N.  For each N, an
     initialization expression (INIT) is computed to create any data
     needed for the test.  If a second expression (F2) is given then
     the execution times of the two expressions are compared.  When
     called without output arguments the results are printed to stdout
     and displayed graphically.

    `F'
          The code expression to evaluate.

    `MAX_N'
          The maximum test length to run.  The default value is 100.
          Alternatively, use `[min_n, max_n]' or specify the N exactly
          with `[n1, n2, ..., nk]'.

    `INIT'
          Initialization expression for function argument values.  Use K
          for the test number and N for the size of the test.  This
          should compute values for all variables used by F.  Note that
          INIT will be evaluated first for k = 0, so things which are
          constant throughout the test series can be computed once.
          The default value is `X = randn (N, 1)'.

    `F2'
          An alternative expression to evaluate, so that the speed of
          two expressions can be directly compared.  The default is
          `[]'.

    `TOL'
          Tolerance used to compare the results of expression F and
          expression F2.  If TOL is positive, the tolerance is an
          absolute one.  If TOL is negative, the tolerance is a
          relative one.  The default is `eps'.  If TOL is `Inf', then
          no comparison will be made.

    `ORDER'
          The time complexity of the expression O(a*n^p).  This is a
          structure with fields `a' and `p'.

    `N'
          The values N for which the expression was calculated *AND*
          the execution time was greater than zero.

    `T_F'
          The nonzero execution times recorded for the expression F in
          seconds.

    `T_F2'
          The nonzero execution times recorded for the expression F2 in
          seconds.  If required, the mean time ratio is simply `mean
          (T_f ./ T_f2)'.


     The slope of the execution time graph shows the approximate power
     of the asymptotic running time O(n^p).  This power is plotted for
     the region over which it is approximated (the latter half of the
     graph).  The estimated power is not very accurate, but should be
     sufficient to determine the general order of an algorithm.  It
     should indicate if, for example, the implementation is
     unexpectedly O(n^2) rather than O(n) because it extends a vector
     each time through the loop rather than pre-allocating storage.  In
     the current version of Octave, the following is not the expected
     O(n).

          speed ("for i = 1:n, y{i} = x(i); endfor", "", [1000, 10000])

     But it is if you preallocate the cell array `y':

          speed ("for i = 1:n, y{i} = x(i); endfor", ...
                 "x = rand (n, 1); y = cell (size (x));", [1000, 10000])

     An attempt is made to approximate the cost of individual
     operations, but it is wildly inaccurate.  You can improve the
     stability somewhat by doing more work for each `n'.  For example:

          speed ("airy(x)", "x = rand (n, 10)", [10000, 100000])

     When comparing two different expressions (F, F2), the slope of the
     line on the speedup ratio graph should be larger than 1 if the new
     expression is faster.  Better algorithms have a shallow slope.
     Generally, vectorizing an algorithm will not change the slope of
     the execution time graph, but will shift it relative to the
     original.  For example:

          speed ("sum (x)", "", [10000, 100000], ...
                 "v = 0; for i = 1:length (x), v += x(i); endfor")

     The following is a more complex example.  If there was an original
     version of `xcorr' using for loops and a second version using an
     FFT, then one could compare the run speed for various lags as
     follows, or for a fixed lag with varying vector lengths as follows:

          speed ("xcorr (x, n)", "x = rand (128, 1);", 100,
                 "xcorr_orig (x, n)", -100*eps)
          speed ("xcorr (x, 15)", "x = rand (20+n, 1);", 100,
                 "xcorr_orig (x, n)", -100*eps)

     Assuming one of the two versions is in xcorr_orig, this would
     compare their speed and their output values.  Note that the FFT
     version is not exact, so one must specify an acceptable tolerance
     on the comparison `100*eps'.  In this case, the comparison should
     be computed relatively, as `abs ((X - Y) ./ Y)' rather than
     absolutely as `abs (X - Y)'.

     Type `example ("speed")' to see some real examples or `demo
     ("speed")' to run them.


File: octave.info,  Node: Tips and Standards,  Next: Contributing Guidelines,  Prev: Test and Demo Functions,  Up: Top

Appendix C Tips and Standards
*****************************

This chapter describes no additional features of Octave.  Instead it
gives advice on making effective use of the features described in the
previous chapters.

* Menu:

* Style Tips::                  Writing clean and robust programs.
* Comment Tips::                Conventions for writing comments.
* Function Headers::            Standard headers for functions.
* Documentation Tips::          Writing readable documentation strings.


File: octave.info,  Node: Style Tips,  Next: Comment Tips,  Up: Tips and Standards

C.1 Writing Clean Octave Programs
=================================

Here are some tips for avoiding common errors in writing Octave code
intended for widespread use:

   * Since all global variables share the same name space, and all
     functions share another name space, you should choose a short word
     to distinguish your program from other Octave programs.  Then take
     care to begin the names of all global variables, constants, and
     functions with the chosen prefix.  This helps avoid name conflicts.

     If you write a function that you think ought to be added to Octave
     under a certain name, such as `fiddle_matrix', don't call it by
     that name in your program.  Call it `mylib_fiddle_matrix' in your
     program, and send mail to <maintainers@octave.org> suggesting that
     it be added to Octave.  If and when it is, the name can be changed
     easily enough.

     If one prefix is insufficient, your package may use two or three
     alternative common prefixes, so long as they make sense.

     Separate the prefix from the rest of the symbol name with an
     underscore `_'.  This will be consistent with Octave itself and
     with most Octave programs.

   * When you encounter an error condition, call the function `error'
     (or `usage').  The `error' and `usage' functions do not return.
     *Note Errors::.

   * Please put a copyright notice on the file if you give copies to
     anyone.  Use the same lines that appear at the top of the function
     files distributed with Octave.  If you have not signed papers to
     assign the copyright to anyone else, then place your name in the
     copyright notice.


File: octave.info,  Node: Comment Tips,  Next: Function Headers,  Prev: Style Tips,  Up: Tips and Standards

C.2 Tips on Writing Comments
============================

Here are the conventions to follow when writing comments.

`#'
     Comments that start with a single sharp-sign, `#', should all be
     aligned to the same column on the right of the source code.  Such
     comments usually explain how the code on the same line does its
     job.  In the Emacs mode for Octave, the `M-;'
     (`indent-for-comment') command automatically inserts such a `#' in
     the right place, or aligns such a comment if it is already present.

`##'
     Comments that start with a double sharp-sign, `##', should be
     aligned to the same level of indentation as the code.  Such
     comments usually describe the purpose of the following lines or
     the state of the program at that point.

The indentation commands of the Octave mode in Emacs, such as `M-;'
(`indent-for-comment') and `TAB' (`octave-indent-line') automatically
indent comments according to these conventions, depending on the number
of semicolons.  *Note Manipulating Comments: (emacs)Comments.


File: octave.info,  Node: Function Headers,  Next: Documentation Tips,  Prev: Comment Tips,  Up: Tips and Standards

C.3 Conventional Headers for Octave Functions
=============================================

Octave has conventions for using special comments in function files to
give information such as who wrote them.  This section explains these
conventions.

   The top of the file should contain a copyright notice, followed by a
block of comments that can be used as the help text for the function.
Here is an example:

     ## Copyright (C) 1996, 1997, 2007 John W. Eaton
     ##
     ## This file is part of Octave.
     ##
     ## Octave is free software; you can redistribute it and/or
     ## modify it under the terms of the GNU General Public
     ## License as published by the Free Software Foundation;
     ## either version 3 of the License, or (at your option) any
     ## later version.
     ##
     ## Octave is distributed in the hope that it will be useful,
     ## but WITHOUT ANY WARRANTY; without even the implied
     ## warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
     ## PURPOSE.  See the GNU General Public License for more
     ## details.
     ##
     ## You should have received a copy of the GNU General Public
     ## License along with Octave; see the file COPYING.  If not,
     ## see <http://www.gnu.org/licenses/>.

     ## usage: [IN, OUT, PID] = popen2 (COMMAND, ARGS)
     ##
     ## Start a subprocess with two-way communication.  COMMAND
     ## specifies the name of the command to start.  ARGS is an
     ## array of strings containing options for COMMAND.  IN and
     ## OUT are the file ids of the input and streams for the
     ## subprocess, and PID is the process id of the subprocess,
     ## or -1 if COMMAND could not be executed.
     ##
     ## Example:
     ##
     ##  [in, out, pid] = popen2 ("sort", "-nr");
     ##  fputs (in, "these\nare\nsome\nstrings\n");
     ##  fclose (in);
     ##  while (ischar (s = fgets (out)))
     ##    fputs (stdout, s);
     ##  endwhile
     ##  fclose (out);

   Octave uses the first block of comments in a function file that do
not appear to be a copyright notice as the help text for the file.  For
Octave to recognize the first comment block as a copyright notice, it
must start with the word `Copyright' after stripping the leading
comment characters.

   After the copyright notice and help text come several "header
comment" lines, each beginning with `## HEADER-NAME:'.  For example,

     ## Author: jwe
     ## Keywords: subprocesses input-output
     ## Maintainer: jwe

   Here is a table of the conventional possibilities for HEADER-NAME:

`Author'
     This line states the name and net address of at least the principal
     author of the library.

          ## Author: John W. Eaton <jwe@octave.org>

`Maintainer'
     This line should contain a single name/address as in the Author
     line, or an address only, or the string `jwe'.  If there is no
     maintainer line, the person(s) in the Author field are presumed to
     be the maintainers.  The example above is mildly bogus because the
     maintainer line is redundant.

     The idea behind the `Author' and `Maintainer' lines is to make
     possible a function to "send mail to the maintainer" without
     having to mine the name out by hand.

     Be sure to surround the network address with `<...>' if you
     include the person's full name as well as the network address.

`Created'
     This optional line gives the original creation date of the file.
     For historical interest only.

`Version'
     If you wish to record version numbers for the individual Octave
     program, put them in this line.

`Adapted-By'
     In this header line, place the name of the person who adapted the
     library for installation (to make it fit the style conventions, for
     example).

`Keywords'
     This line lists keywords.  Eventually, it will be used by an
     apropos command to allow people will find your package when
     they're looking for things by topic area.  To separate the
     keywords, you can use spaces, commas, or both.

   Just about every Octave function ought to have the `Author' and
`Keywords' header comment lines.  Use the others if they are
appropriate.  You can also put in header lines with other header
names--they have no standard meanings, so they can't do any harm.


File: octave.info,  Node: Documentation Tips,  Prev: Function Headers,  Up: Tips and Standards

C.4 Tips for Documentation Strings
==================================

As noted above, documentation is typically in a commented header block
on an Octave function following the copyright statement.  The help
string shown above is an unformatted string and will be displayed as is
by Octave.  Here are some tips for the writing of documentation strings.

   * Every command, function, or variable intended for users to know
     about should have a documentation string.

   * An internal variable or subroutine of an Octave program might as
     well have a documentation string.

   * The first line of the documentation string should consist of one
     or two complete sentences that stand on their own as a summary.

     The documentation string can have additional lines that expand on
     the details of how to use the function or variable.  The
     additional lines should also be made up of complete sentences.

   * For consistency, phrase the verb in the first sentence of a
     documentation string as an infinitive with "to" omitted.  For
     instance, use "Return the frob of A and B." in preference to
     "Returns the frob of A and B."  Usually it looks good to do
     likewise for the rest of the first paragraph.  Subsequent
     paragraphs usually look better if they have proper subjects.

   * Write documentation strings in the active voice, not the passive,
     and in the present tense, not the future.  For instance, use
     "Return a list containing A and B." instead of "A list containing
     A and B will be returned."

   * Avoid using the word "cause" (or its equivalents) unnecessarily.
     Instead of, "Cause Octave to display text in boldface," just write
     "Display text in boldface."

   * Use two spaces between the period marking the end of a sentence
     and the word which opens the next sentence.  This convention has
     no effect for typeset formats like TeX, but improves the
     readability of the documentation in fixed-width environments such
     as the Info reader.

   * Do not start or end a documentation string with whitespace.

   * Format the documentation string so that it fits within an
     80-column screen.  It is a good idea for most lines to be no wider
     than 60 characters.

     However, rather than simply filling the entire documentation
     string, you can make it much more readable by choosing line breaks
     with care.  Use blank lines between topics if the documentation
     string is long.

   * *Do not* indent subsequent lines of a documentation string so that
     the text is lined up in the source code with the text of the first
     line.  This looks nice in the source code, but looks bizarre when
     users view the documentation.  Remember that the indentation
     before the starting double-quote is not part of the string!

   * When choosing variable names try to adhere to the following
     guidelines.


          vectors : x,y,z,t,w


          matrices : A,B,M


          strings : str,s


          filenames : fname


          cells,cellstrs : c,cstr

   * The documentation string for a variable that is a yes-or-no flag
     should start with words such as "Nonzero means...", to make it
     clear that all nonzero values are equivalent and indicate
     explicitly what zero and nonzero mean.

   * When a function's documentation string mentions the value of an
     argument of the function, use the argument name in capital letters
     as if it were a name for that value.  Thus, the documentation
     string of the operator `/' refers to its second argument as
     `DIVISOR', because the actual argument name is `divisor'.

     Also use all caps for meta-syntactic variables, such as when you
     show the decomposition of a list or vector into subunits, some of
     which may vary.

   Octave also allows extensive formatting of the help string of
functions using Texinfo.  The effect on the online documentation is
relatively small, but makes the help string of functions conform to the
help of Octave's own functions.  However, the effect on the appearance
of printed or online documentation will be greatly improved.

   The fundamental building block of Texinfo documentation strings is
the Texinfo-macro `@deftypefn', which takes three arguments: The class
the function is in, its output arguments, and the function's signature.
Typical classes for functions include `Function File' for standard
Octave functions, and `Loadable Function' for dynamically linked
functions.  A skeletal Texinfo documentation string therefore looks
like this

     -*- texinfo -*-
     @deftypefn{Function File} {@var{ret} =} fn (...)
     @cindex index term
     Help text in Texinfo format.  Code samples should be marked
     like @code{sample of code} and variables should be marked
     as @var{variable}.
     @seealso{fn2}
     @end deftypefn

   This help string must be commented in user functions, or in the help
string of the `DEFUN_DLD' macro for dynamically loadable functions.
The important aspects of the documentation string are

-*- texinfo -*-
     This string signals Octave that the following text is in Texinfo
     format, and should be the first part of any help string in Texinfo
     format.

@deftypefn{class} ... @end deftypefn
     The entire help string should be enclosed within the block defined
     by deftypefn.

@cindex index term
     This generates an index entry, and can be useful when the function
     is included as part of a larger piece of documentation.  It is
     ignored within Octave's help viewer.  Only one index term may
     appear per line but multiple @cindex lines are valid if the
     function should be filed under different terms.

@var{variable}
     All variables should be marked with this macro.  The markup of
     variables is then changed appropriately for display.

@code{sample of code}
     All samples of code should be marked with this macro for the same
     reasons as the @var macro.

@seealso{function2}
     This is a comma separated list of function names that allows cross
     referencing from one function documentation string to another.

   Texinfo format has been designed to generate output for online
viewing with text terminals as well as generating high-quality printed
output.  To these ends, Texinfo has commands which control the
diversion of parts of the document into a particular output processor.
Three formats are of importance: info, HTML and TeX.  These are
selected with

     @ifinfo
     Text area for info only
     @end ifinfo

     @ifhtml
     Text area for HTML only
     @end ifhtml

     @tex
     Text area for TeX only
     @end tex

   Note that often TeX output can be used in HTML documents and so often
the `@ifhtml' blocks are unnecessary.  If no specific output processor
is chosen, by default, the text goes into all output processors.  It is
usual to have the above blocks in pairs to allow the same information
to be conveyed in all output formats, but with a different markup.
Currently, most Octave documentation only makes a distinction between
TeX and all other formats.  Therefore, the following construct is seen
repeatedly.

     @tex
     text for TeX only
     @end tex
     @ifnottex
     text for info, HTML, plaintext
     @end ifnottex

   Another important feature of Texinfo that is often used in Octave
help strings is the `@example' environment.  An example of its use is

     @example
     @group
     @code{2 * 2}
     @result{} 4
     @end group
     @end example

which produces

     `2 * 2'
     => 4

   The `@group' block prevents the example from being split across a
page boundary, while the `@result{}' macro produces a right arrow
signifying the result of a command.  If your example is larger than 20
lines it is better NOT to use grouping so that a reasonable page
boundary can be calculated.

   In many cases a function has multiple ways in which it can be called,
and the `@deftypefnx' macro can be used to give alternatives.  For
example

     -*- texinfo -*-
     @deftypefn {Function File} {@var{a} =} fn (@var{x}, ...)
     @deftypefnx{Function File} {@var{a} =} fn (@var{y}, ...)
     Help text in Texinfo format.
     @end deftypefn

   Many complete examples of Texinfo documentation can be taken from the
help strings for the Octave functions themselves.  A relatively complete
example of which is the `nchoosek' function.  The Texinfo documentation
string for `nchoosek' is

     -*- texinfo -*-
     @deftypefn  {Function File} {@var{c} =} nchoosek (@var{n}, @var{k})
     @deftypefnx {Function File} {@var{c} =} nchoosek (@var{set}, @var{k})

     Compute the binomial coefficient or all combinations of a set of items.

     If @var{n} is a scalar then calculate the binomial coefficient
     of @var{n} and @var{k} which is defined as
     @tex
     $$
      {n \choose k} = {n (n-1) (n-2) \cdots (n-k+1) \over k!}
                    = {n! \over k! (n-k)!}
     $$
     @end tex
     @ifnottex

     @example
     @group
      /   \
      | n |    n (n-1) (n-2) @dots{} (n-k+1)       n!
      |   |  = ------------------------- =  ---------
      | k |               k!                k! (n-k)!
      \   /
     @end group
     @end example

     @end ifnottex
     @noindent
     This is the number of combinations of @var{n} items taken in groups of
     size @var{k}.

     If the first argument is a vector, @var{set}, then generate all
     combinations of the elements of @var{set}, taken @var{k} at a time, with
     one row per combination.  The result @var{c} has @var{k} columns and
     @w{@code{nchoosek (length (@var{set}), @var{k})}} rows.

     For example:

     How many ways can three items be grouped into pairs?

     @example
     @group
     nchoosek (3, 2)
        @result{} 3
     @end group
     @end example

     What are the possible pairs?

     @example
     @group
     nchoosek (1:3, 2)
        @result{}  1   2
            1   3
            2   3
     @end group
     @end example

     @code{nchoosek} works only for non-negative, integer arguments.  Use
     @code{bincoeff} for non-integer and negative scalar arguments, or for
     computing many binomial coefficients at once with vector inputs
     for @var{n} or @var{k}.

     @seealso{bincoeff, perms}
     @end deftypefn
   which demonstrates most of the concepts discussed above.


File: octave.info,  Node: Contributing Guidelines,  Next: Obsolete Functions,  Prev: Tips and Standards,  Up: Top

Appendix D Contributing Guidelines
**********************************

This chapter is dedicated to those who wish to contribute code to
Octave.

* Menu:

* How to Contribute::
* Building the Development Sources::
* Basics of Generating a Changeset::
* General Guidelines::
* Octave Sources (m-files)::
* C++ Sources::
* Other Sources::


File: octave.info,  Node: How to Contribute,  Next: Building the Development Sources,  Up: Contributing Guidelines

D.1 How to Contribute
=====================

The mailing list for Octave development discussion and sending
contributions is <maintainers@octave.org>.  This concerns the
development of Octave core, i.e., code that goes to Octave directly.
You may consider developing and publishing a package instead; a great
place for this is the allied Octave-Forge project
(`http://octave.sf.net').  Note that the Octave project is inherently
more conservative and follows narrower rules.


File: octave.info,  Node: Building the Development Sources,  Next: Basics of Generating a Changeset,  Prev: How to Contribute,  Up: Contributing Guidelines

D.2 Building the Development Sources
====================================

In addition to all the tools (both optional and required) that are
listed in *note Build Dependencies:: you will need:

Mercurial
     Distributed version control system
     (`http://mercurial.selenic.com').  Octave's sources are stored in
     a Mercurial archive.

Git
     Distributed version control system (`http://git-scm.com').  The
     gnulib sources that Octave depends on are stored in a Git archive.

   Once you have the required tools installed, you can build Octave by
doing

   * Check out a copy of the Octave sources:
          hg clone http://hg.savannah.gnu.org/hgweb/octave

   * Change to the top-level directory of the newly checked out sources:
          cd octave

   * Generate the necessary configuration files:
          ./autogen.sh

   * Create a build directory and change to it:
          mkdir build
          cd build
     By using a separate build directory, you will keep the source
     directory clean and it will be easy to completely remove all files
     generated by the build.  You can also have parallel build trees
     for different purposes that all share the same sources.  For
     example, one build tree may be configured to disable compiler
     optimization in order to allow for easier debugging while another
     may be configured to test building with other specialized compiler
     flags.

   * Run Octave's configure script from the build directory:
          ../configure

   * Run make in the build directory:
          make

   Once the build is finished, you will see a message like the
following:

     Octave successfully built.  Now choose from the following:

        ./run-octave    - to run in place to test before installing
        make check      - to run the tests
        make install    - to install (PREFIX=...)


File: octave.info,  Node: Basics of Generating a Changeset,  Next: General Guidelines,  Prev: Building the Development Sources,  Up: Contributing Guidelines

D.3 Basics of Generating a Changeset
====================================

The preferable form of contribution is creating a Mercurial changeset
and sending it via e-mail to the octave-maintainers mailing list.
Mercurial is the source code management system currently used to develop
Octave.  Other forms of contributions (e.g., simple diff patches) are
also acceptable, but they slow down the review process.  If you want to
make more contributions, you should really get familiar with Mercurial.
A good place to start is
`http://www.selenic.com/mercurial/wiki/index.cgi/Tutorial'.  There you
will also find help how to install Mercurial.

   A simple contribution sequence could look like this:

     hg clone http://www.octave.org/hg/octave
                                  # make a local copy of the octave
                                  # source repository
     cd octave
     # change some sources...
     hg commit -m "make Octave the coolest software ever"
                                  # commit the changeset into your
                                  # local repository
     hg export -o ../cool.diff tip
                                  # export the changeset to a diff
                                  # file
     # send ../cool.diff via email

   You may want to get familiar with Mercurial queues to manage your
changesets.  Here is a slightly more complex example using Mercurial
queues, where work on two unrelated changesets is done in parallel and
one of the changesets is updated after discussion on the maintainers
mailing list:

     hg qnew nasty_bug            # create a new patch
     # change sources...
     hg qref                      # save the changes into the patch
     # change even more...
     hg qref -m "solution to nasty bug!"
                                  # save again with commit message
     hg export -o ../nasty.diff tip
                                  # export the patch
     # send ../nasty.diff via email
     hg qpop                      # undo the application of the patch
                                  # and remove the changes from the
                                  # source tree
     hg qnew doc_improvements     # create an unrelated patch
     # change doc sources...
     hg qref -m "could not find myfav.m in the doc"
                                  # save the changes into the patch
     hg export -o ../doc.diff tip
                                  # export the second patch
     # send ../doc.diff tip via email
     hg qpop
     # discussion in the maintainers mailing list ...
     hg qpush nasty_bug           # apply the patch again
     # change sources yet again ...
     hg qref
     hg export -o ../nasty2.diff tip
     # send ../nasty2.diff via email


File: octave.info,  Node: General Guidelines,  Next: Octave Sources (m-files),  Prev: Basics of Generating a Changeset,  Up: Contributing Guidelines

D.4 General Guidelines
======================

All Octave's sources are distributed under the General Public License
(GPL).  Currently, Octave uses GPL version 3.  For details about this
license, see `http://www.gnu.org/licenses/gpl.html'.  Therefore,
whenever you create a new source file, it should have the following
comment header (use appropriate year, name and comment marks):

     ## Copyright (C) 1996-2012 John W. Eaton <jwe@octave.org>
     ##
     ## This file is part of Octave.
     ##
     ## Octave is free software; you can redistribute it and/or
     ## modify it under the terms of the GNU General Public
     ## License as published by the Free Software Foundation;
     ## either version 3 of the License, or (at your option) any
     ## later version.
     ##
     ## Octave is distributed in the hope that it will be useful,
     ## but WITHOUT ANY WARRANTY; without even the implied
     ## warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
     ## PURPOSE.  See the GNU General Public License for more
     ## details.
     ##
     ## You should have received a copy of the GNU General Public
     ## License along with Octave; see the file COPYING.  If not,
     ## see <http://www.gnu.org/licenses/>.

   Always include commit messages in changesets.  After making your
source changes, record and briefly describe the changes in your commit
message.  You should have previously configured your `.hgrc' (or
`Mercurial.ini' on Windows) with your name and email, which will get
automatically added to your commit message.  Your commit message should
have a brief one-line explanation of what the commit does.  If you are
patching a bug, this one-line explanation should mention the bug number
at the end.  If your change is small and only touches one file, this is
typically sufficient.  If you are modifying several files or several
parts of one file, you should enumerate your changes roughly following
the GNU coding standards on changelogs, like the following example:

     look for methods before constructors

     * symtab.cc (symbol_table::fcn_info::fcn_info_rep::find):
     Look for class methods before constructors, contrary to MATLAB
     documentation.

     * test/ctor-vs-method: New directory of test classes.
     * test/test_ctor_vs_method.m: New file.
     * test/Makefile.am: Include ctor-vs-method/module.mk.
     (FCN_FILES): Include test_ctor_vs_method.m in the list.

In this example, the names of files is mentioned, and in parentheses the
name of the function in that file that was modified.  There is no need
to mention the function for m-files that only contain one function.  The
commit message should describe what is changed, not why.  Any
explanation of why a change is needed should appear as comments in the
code, particularly if there is something that might not be obvious to
someone reading it later.

   When submitting code which addresses a known bug on the Octave bug
tracker (`http://bugs.octave.org'), please add '(bug #XXXXX)' to the
first line of the commit messages.  For example:

     Fix bug for complex input for gradient (bug #34292).

   The preferred comment mark for places that may need further
attention is FIXME.


File: octave.info,  Node: Octave Sources (m-files),  Next: C++ Sources,  Prev: General Guidelines,  Up: Contributing Guidelines

D.5 Octave Sources (m-files)
============================

Don't use tabs.  Tabs cause trouble.  If you are used to them, set up
your editor so that it converts tabs to spaces.  Indent the bodies of
the statement blocks.  Recommended indent is 2 spaces.  When calling
functions, put spaces after commas and before the calling parentheses,
like this:

       x = max (sin (y+3), 2);

An exception are matrix and vector constructors:

       [sin(x), cos(x)]

Here, putting spaces after `sin', `cos' would result in a parse error.
In indexing expression, do not put a space after the identifier (this
differentiates indexing and function calls nicely).  The space after
comma is not necessary if index expressions are simple, i.e., you may
write

       A(:,i,j)

but

       A([1:i-1;i+1:n], XI(:,2:n-1))

   Use lowercase names if possible.  Uppercase is acceptable for
variable names consisting of 1-2 letters.  Do not use mixed case names.
Function names must be lowercase.  Function names are global, so choose
them wisely.

   Always use a specific end-of-block statement (like `endif',
`endswitch') rather than generic `end'.

   Enclose the `if', `while', `until' and `switch' conditions in
parentheses, like in C:

     if (isvector (a))
       s = sum(a);
     endif

Do not do this, however, with the iteration counter portion of a `for'
statement.  Write:

     for i = 1:n
       b(i) = sum (a(:,i));
     endfor


File: octave.info,  Node: C++ Sources,  Next: Other Sources,  Prev: Octave Sources (m-files),  Up: Contributing Guidelines

D.6 C++ Sources
===============

Don't use tabs.  Tabs cause trouble.  If you are used to them, set up
your editor so that it converts tabs to spaces.  Format function headers
like this:

     static bool
     matches_patterns (const string_vector& patterns, int pat_idx,
                       int num_pat, const std::string& name)

The function name should start in column 1, and multi-line argument
lists should be aligned on the first char after the open parenthesis.
You should put a space after the left open parenthesis and after commas,
for both function definitions and function calls.

   Recommended indent is 2 spaces.  When indenting, indent the statement
after control structures (like `if', `while', etc.).  If there is a
compound statement, indent _both_ the curly braces and the body of the
statement (so that the body gets indented by _two_ indents).  Example:

     if (have_args)
       {
         idx.push_back (first_args);
         have_args = false;
       }
     else
       idx.push_back (make_value_list (*p_args, *p_arg_nm, &tmp));

If you have nested `if' statements, use extra braces for extra
clarification.

   Split long expressions in such a way that a continuation line starts
with an operator rather than identifier.  If the split occurs inside
braces, continuation should be aligned with the first char after the
innermost braces enclosing the split.  Example:

     SVD::type type = ((nargout == 0 || nargout == 1)
                       ? SVD::sigma_only
                       : (nargin == 2) ? SVD::economy : SVD::std);

Consider putting extra braces around a multiline expression to make it
more readable, even if they are not necessary.  Also, do not hesitate to
put extra braces anywhere if it improves clarity.

   Declare variables just before they're needed.  Use local variables of
blocks--it helps optimization.  Don't write multi-line variable
declaration with a single type specification and multiple variables.  If
the variables don't fit on single line, repeat the type specification.
Example:

     octave_value retval;

     octave_idx_type nr = b.rows ();
     octave_idx_type nc = b.cols ();

     double d1, d2;

   Use lowercase names if possible.  Uppercase is acceptable for
variable names consisting of 1-2 letters.  Do not use mixed case names.

   Use Octave's types and classes if possible.  Otherwise, use the C++
standard library.  Use of STL containers and algorithms is encouraged.
Use templates wisely to reduce code duplication.  Avoid comma
expressions, labels and gotos, and explicit typecasts.  If you need to
typecast, use the modern C++ casting operators.  In functions, minimize
the number of `return' statements--use nested `if' statements if
possible.


File: octave.info,  Node: Other Sources,  Prev: C++ Sources,  Up: Contributing Guidelines

D.7 Other Sources
=================

Apart from C++ and Octave language (m-files), Octave's sources include
files written in C, Fortran, M4, Perl, Unix shell, AWK, Texinfo and
TeX.  There are not many rules to follow when using these other
languages; some of them are summarized below.  In any case, the golden
rule is: if you modify a source file, try to follow any conventions you
can detect in the file or other similar files.

   For C you should obviously follow all C++ rules that can apply.

   If you modify a Fortran file, you should stay within Fortran 77 with
common extensions like `END DO'.  Currently, we want all sources to be
compilable with the f2c and g77 compilers, without special flags if
possible.  This usually means that non-legacy compilers also accept the
sources.

   The M4 macro language is mainly used for Autoconf configuration
files.  You should follow normal M4 rules when contributing to these
files.  Some M4 files come from external source, namely the Autoconf
archive `http://autoconf-archive.cryp.to'.

   If you give a code example in the documentation written in Texinfo
with the `@example' environment, you should be aware that the text
within such an environment will not be wrapped.  It is recommended that
you keep the lines short enough to fit on pages in the generated pdf or
ps documents.  Here is a ruler (in an `@example' environment) for
finding the appropriate line width:

              1         2         3         4         5         6
     123456789012345678901234567890123456789012345678901234567890


File: octave.info,  Node: Obsolete Functions,  Next: Trouble,  Prev: Contributing Guidelines,  Up: Top

Appendix E Obsolete Functions
*****************************

After being marked as deprecated for two major releases, the following
functions have been removed from Octave.  The third column of the table
shows the version of Octave in which the function was removed.  Prior to
removal, each function in the list was marked as deprecated for at least
two major releases.  All deprecated functions issue warnings explaining
that they will be removed in a future version of Octave, and which
function should be used instead.

   Replacement functions do not always accept precisely the same
arguments as the obsolete function, but should provide equivalent
functionality.

Obsolete Function      Replacement            Version
---------------------------------------------------------- 
`beta_cdf'             `betacdf'              3.4.0
`beta_inv'             `betainv'              3.4.0
`beta_pdf'             `betapdf'              3.4.0
`beta_rnd'             `betarnd'              3.4.0
`binomial_cdf'         `binocdf'              3.4.0
`binomial_inv'         `binoinv'              3.4.0
`binomial_pdf'         `binopdf'              3.4.0
`binomial_rnd'         `binornd'              3.4.0
`chisquare_cdf'        `chi2cdf'              3.4.0
`chisquare_inv'        `chi2inv'              3.4.0
`chisquare_pdf'        `chi2pdf'              3.4.0
`chisquare_rnd'        `chi2rnd'              3.4.0
`clearplot'            `clf'                  3.4.0
`com2str'              `num2str'              3.4.0
`exponential_cdf'      `expcdf'               3.4.0
`exponential_inv'      `expinv'               3.4.0
`exponential_pdf'      `exppdf'               3.4.0
`exponential_rnd'      `exprnd'               3.4.0
`f_cdf'                `fcdf'                 3.4.0
`f_inv'                `finv'                 3.4.0
`f_pdf'                `fpdf'                 3.4.0
`f_rnd'                `frnd'                 3.4.0
`gamma_cdf'            `gamcdf'               3.4.0
`gamma_inv'            `gaminv'               3.4.0
`gamma_pdf'            `gampdf'               3.4.0
`gamma_rnd'            `gamrnd'               3.4.0
`geometric_cdf'        `geocdf'               3.4.0
`geometric_inv'        `geoinv'               3.4.0
`geometric_pdf'        `geopdf'               3.4.0
`geometric_rnd'        `geornd'               3.4.0
`hypergeometric_cdf'   `hygecdf'              3.4.0
`hypergeometric_inv'   `hygeinv'              3.4.0
`hypergeometric_pdf'   `hygepdf'              3.4.0
`hypergeometric_rnd'   `hygernd'              3.4.0
`intersection'         `intersect'            3.4.0
`is_bool'              `isbool'               3.4.0
`is_complex'           `iscomplex'            3.4.0
`is_list'              `islist'               3.4.0
`is_matrix'            `ismatrix'             3.4.0
`is_scalar'            `isscalar'             3.4.0
`is_square'            `issquare'             3.4.0
`is_stream'            `isstream'             3.4.0
`is_struct'            `isstruct'             3.4.0
`is_symmetric'         `issymmetric'          3.4.0
`is_vector'            `isvector'             3.4.0
`lognormal_cdf'        `logncdf'              3.4.0
`lognormal_inv'        `logninv'              3.4.0
`lognormal_pdf'        `lognpdf'              3.4.0
`lognormal_rnd'        `lognrnd'              3.4.0
`meshdom'              `meshgrid'             3.4.0
`normal_cdf'           `normcdf'              3.4.0
`normal_inv'           `norminv'              3.4.0
`normal_pdf'           `normpdf'              3.4.0
`normal_rnd'           `normrnd'              3.4.0
`pascal_cdf'           `nbincdf'              3.4.0
`pascal_inv'           `nbininv'              3.4.0
`pascal_pdf'           `nbinpdf'              3.4.0
`pascal_rnd'           `nbinrnd'              3.4.0
`poisson_cdf'          `poisscdf'             3.4.0
`poisson_inv'          `poissinv'             3.4.0
`poisson_pdf'          `poisspdf'             3.4.0
`poisson_rnd'          `poissrnd'             3.4.0
`polyinteg'            `polyint'              3.4.0
`struct_contains'      `isfield'              3.4.0
`struct_elements'      `fieldnames'           3.4.0
`t_cdf'                `tcdf'                 3.4.0
`t_inv'                `tinv'                 3.4.0
`t_pdf'                `tpdf'                 3.4.0
`t_rnd'                `trnd'                 3.4.0
`uniform_cdf'          `unifcdf'              3.4.0
`uniform_inv'          `unifinv'              3.4.0
`uniform_pdf'          `unifpdf'              3.4.0
`uniform_rnd'          `unifrnd'              3.4.0
`weibull_cdf'          `wblcdf'               3.4.0
`weibull_inv'          `wblinv'               3.4.0
`weibull_pdf'          `wblpdf'               3.4.0
`weibull_rnd'          `wblrnd'               3.4.0
`wiener_rnd'           `wienrnd'              3.4.0
`create_set'           `unique'               3.6.0
`dmult'                `diag (A) * B'         3.6.0
`iscommand'            None                   3.6.0
`israwcommand'         None                   3.6.0
`lchol'                `chol (..., "lower")'  3.6.0
`loadimage'            `load' or `imread'     3.6.0
`mark_as_command'      None                   3.6.0
`mark_as_rawcommand'   None                   3.6.0
`spatan2'              `atan2'                3.6.0
`spchol'               `chol'                 3.6.0
`spchol2inv'           `chol2inv'             3.6.0
`spcholinv'            `cholinv'              3.6.0
`spcumprod'            `cumprod'              3.6.0
`spcumsum'             `cumsum'               3.6.0
`spdet'                `det'                  3.6.0
`spdiag'               `sparse (diag (...))'  3.6.0
`spfind'               `find'                 3.6.0
`sphcat'               `horzcat'              3.6.0
`spinv'                `inv'                  3.6.0
`spkron'               `kron'                 3.6.0
`splchol'              `chol (..., "lower")'  3.6.0
`split'                `char (strsplit (s,    3.6.0
                       t))'                   
`splu'                 `lu'                   3.6.0
`spmax'                `max'                  3.6.0
`spmin'                `min'                  3.6.0
`spprod'               `prod'                 3.6.0
`spqr'                 `qr'                   3.6.0
`spsum'                `sum'                  3.6.0
`spsumsq'              `sumsq'                3.6.0
`spvcat'               `vertcat'              3.6.0
`str2mat'              `char'                 3.6.0
`unmark_command'       None                   3.6.0
`unmark_rawcommand'    None                   3.6.0


File: octave.info,  Node: Trouble,  Next: Installation,  Prev: Obsolete Functions,  Up: Top

Appendix F Known Causes of Trouble
**********************************

   This section describes known problems that affect users of Octave.
Most of these are not Octave bugs per se--if they were, we would fix
them.  But the result for a user may be like the result of a bug.

   Some of these problems are due to bugs in other software, some are
missing features that are too much work to add, and some are places
where people's opinions differ as to what is best.

* Menu:

* Actual Bugs::                 Bugs we will fix later.
* Reporting Bugs::
* Service::


File: octave.info,  Node: Actual Bugs,  Next: Reporting Bugs,  Up: Trouble

F.1 Actual Bugs We Haven't Fixed Yet
====================================

   * Output that comes directly from Fortran functions is not sent
     through the pager and may appear out of sequence with other output
     that is sent through the pager.  One way to avoid this is to force
     pending output to be flushed before calling a function that will
     produce output from within Fortran functions.  To do this, use the
     command

          fflush (stdout)

     Another possible workaround is to use the command

          page_screen_output (false);

     to turn the pager off.

   A list of ideas for future enhancements is distributed with Octave.
See the file `PROJECTS' in the top level directory in the source
distribution.


File: octave.info,  Node: Reporting Bugs,  Next: Service,  Prev: Actual Bugs,  Up: Trouble

F.2 Reporting Bugs
==================

Your bug reports play an essential role in making Octave reliable.

   When you encounter a problem, the first thing to do is to see if it
is already known.  *Note Trouble::.  If it isn't known, then you should
report the problem.

   Reporting a bug may help you by bringing a solution to your problem,
or it may not.  In any case, the principal function of a bug report is
to help the entire community by making the next version of Octave work
better.  Bug reports are your contribution to the maintenance of Octave.

   In order for a bug report to serve its purpose, you must include the
information that makes it possible to fix the bug.

* Menu:

* Bug Criteria::
* Bug Tracker::        Where to submit your bug report.
* Bug Reporting::      How to report a bug effectively.
* Sending Patches::    How to send a patch for Octave.


File: octave.info,  Node: Bug Criteria,  Next: Bug Tracker,  Up: Reporting Bugs

F.2.1 Have You Found a Bug?
---------------------------

If you are not sure whether you have found a bug, here are some
guidelines:

   * If Octave gets a fatal signal, for any input whatever, that is a
     bug.  Reliable interpreters never crash.

   * If Octave produces incorrect results, for any input whatever, that
     is a bug.

   * Some output may appear to be incorrect when it is in fact due to a
     program whose behavior is undefined, which happened by chance to
     give the desired results on another system.  For example, the
     range operator may produce different results because of
     differences in the way floating point arithmetic is handled on
     various systems.

   * If Octave produces an error message for valid input, that is a bug.

   * If Octave does not produce an error message for invalid input,
     that is a bug.  However, you should note that your idea of
     "invalid input" might be my idea of "an extension" or "support for
     traditional practice".

   * If you are an experienced user of programs like Octave, your
     suggestions for improvement are welcome in any case.


File: octave.info,  Node: Bug Tracker,  Next: Bug Reporting,  Prev: Bug Criteria,  Up: Reporting Bugs

F.2.2 Where to Report Bugs
--------------------------

To report a bug in Octave, submit a bug report to the Octave bug tracker
`http://bugs.octave.org'.

   *Do not send bug reports to `help-octave'*.  Most users of Octave do
not want to receive bug reports.


File: octave.info,  Node: Bug Reporting,  Next: Sending Patches,  Prev: Bug Tracker,  Up: Reporting Bugs

F.2.3 How to Report Bugs
------------------------

Submit bug reports for Octave to the Octave bug tracker
`http://bugs.octave.org'.

   The fundamental principle of reporting bugs usefully is this:
*report all the facts*.  If you are not sure whether to state a fact or
leave it out, state it!

   Often people omit facts because they think they know what causes the
problem and they conclude that some details don't matter.  Thus, you
might assume that the name of the variable you use in an example does
not matter.  Well, probably it doesn't, but one cannot be sure.
Perhaps the bug is a stray memory reference which happens to fetch from
the location where that name is stored in memory; perhaps, if the name
were different, the contents of that location would fool the
interpreter into doing the right thing despite the bug.  Play it safe
and give a specific, complete example.

   Keep in mind that the purpose of a bug report is to enable someone to
fix the bug if it is not known.  Always write your bug reports on the
assumption that the bug is not known.

   Sometimes people give a few sketchy facts and ask, "Does this ring a
bell?"  This cannot help us fix a bug.  It is better to send a complete
bug report to begin with.

   Try to make your bug report self-contained.  If we have to ask you
for more information, it is best if you include all the previous
information in your response, as well as the information that was
missing.

   To enable someone to investigate the bug, you should include all
these things:

   * The version of Octave.  You can get this by noting the version
     number that is printed when Octave starts, or running it with the
     `-v' option.

   * A complete input file that will reproduce the bug.

     A single statement may not be enough of an example--the bug might
     depend on other details that are missing from the single statement
     where the error finally occurs.

   * The command arguments you gave Octave to execute that example and
     observe the bug.  To guarantee you won't omit something important,
     list all the options.

     If we were to try to guess the arguments, we would probably guess
     wrong and then we would not encounter the bug.

   * The type of machine you are using, and the operating system name
     and version number.

   * The command-line arguments you gave to the `configure' command when
     you installed the interpreter.

   * A complete list of any modifications you have made to the
     interpreter source.

     Be precise about these changes--show a context diff for them.

   * Details of any other deviations from the standard procedure for
     installing Octave.

   * A description of what behavior you observe that you believe is
     incorrect.  For example, "The interpreter gets a fatal signal,"
     or, "The output produced at line 208 is incorrect."

     Of course, if the bug is that the interpreter gets a fatal signal,
     then one can't miss it.  But if the bug is incorrect output, we
     might not notice unless it is glaringly wrong.

     Even if the problem you experience is a fatal signal, you should
     still say so explicitly.  Suppose something strange is going on,
     such as, your copy of the interpreter is out of sync, or you have
     encountered a bug in the C library on your system.  Your copy
     might crash and the copy here would not.  If you said to expect a
     crash, then when the interpreter here fails to crash, we would
     know that the bug was not happening.  If you don't say to expect a
     crash, then we would not know whether the bug was happening.  We
     would not be able to draw any conclusion from our observations.

     Often the observed symptom is incorrect output when your program
     is run.  Unfortunately, this is not enough information unless the
     program is short and simple.  It is very helpful if you can
     include an explanation of the expected output, and why the actual
     output is incorrect.

   * If you wish to suggest changes to the Octave source, send them as
     context diffs.  If you even discuss something in the Octave source,
     refer to it by context, not by line number, because the line
     numbers in the development sources probably won't match those in
     your sources.

   Here are some things that are not necessary:

   * A description of the envelope of the bug.

     Often people who encounter a bug spend a lot of time investigating
     which changes to the input file will make the bug go away and
     which changes will not affect it.  Such information is usually not
     necessary to enable us to fix bugs in Octave, but if you can find
     a simpler example to report _instead_ of the original one, that is
     a convenience.  Errors in the output will be easier to spot,
     running under the debugger will take less time, etc.  Most Octave
     bugs involve just one function, so the most straightforward way to
     simplify an example is to delete all the function definitions
     except the one in which the bug occurs.

     However, simplification is not vital; if you don't want to do
     this, report the bug anyway and send the entire test case you used.

   * A patch for the bug.  Patches can be helpful, but if you find a
     bug, you should report it, even if you cannot send a fix for the
     problem.


File: octave.info,  Node: Sending Patches,  Prev: Bug Reporting,  Up: Reporting Bugs

F.2.4 Sending Patches for Octave
--------------------------------

If you would like to write bug fixes or improvements for Octave, that is
very helpful.  When you send your changes, please follow these
guidelines to avoid causing extra work for us in studying the patches.

   If you don't follow these guidelines, your information might still be
useful, but using it will take extra work.  Maintaining Octave is a lot
of work in the best of circumstances, and we can't keep up unless you do
your best to help.

   * Send an explanation with your changes of what problem they fix or
     what improvement they bring about.  For a bug fix, just include a
     copy of the bug report, and explain why the change fixes the bug.

   * Always include a proper bug report for the problem you think you
     have fixed.  We need to convince ourselves that the change is
     right before installing it.  Even if it is right, we might have
     trouble judging it if we don't have a way to reproduce the problem.

   * Include all the comments that are appropriate to help people
     reading the source in the future understand why this change was
     needed.

   * Don't mix together changes made for different reasons.  Send them
     _individually_.

     If you make two changes for separate reasons, then we might not
     want to install them both.  We might want to install just one.

   * Use `diff -c' to make your diffs.  Diffs without context are hard
     for us to install reliably.  More than that, they make it hard for
     us to study the diffs to decide whether we want to install them.
     Unified diff format is better than contextless diffs, but not as
     easy to read as `-c' format.

     If you have GNU diff, use `diff -cp', which shows the name of the
     function that each change occurs in.

   * Write the change log entries for your changes.

     Read the `ChangeLog' file to see what sorts of information to put
     in, and to learn the style that we use.  The purpose of the change
     log is to show people where to find what was changed.  So you need
     to be specific about what functions you changed; in large
     functions, it's often helpful to indicate where within the
     function the change was made.

     On the other hand, once you have shown people where to find the
     change, you need not explain its purpose.  Thus, if you add a new
     function, all you need to say about it is that it is new.  If you
     feel that the purpose needs explaining, it probably does--but the
     explanation will be much more useful if you put it in comments in
     the code.

     If you would like your name to appear in the header line for who
     made the change, send us the header line.


File: octave.info,  Node: Service,  Prev: Reporting Bugs,  Up: Trouble

F.3 How To Get Help with Octave
===============================

The mailing list <help@octave.org> exists for the discussion of matters
related to using and installing Octave.  If would like to join the
discussion, please send a short note to <help-request@octave.org>.

   *Please do not* send requests to be added or removed from the
mailing list, or other administrative trivia to the list itself.

   If you think you have found a bug in Octave or in the installation
procedure, however, you should submit a complete bug report to the
Octave bug tracker at `http://bugs.octave.org'.  But before you submit
a bug report, please read `http://www.octave.org/bugs.html' to learn
how to submit a useful bug report.


File: octave.info,  Node: Installation,  Next: Emacs Octave Support,  Prev: Trouble,  Up: Top

Appendix G Installing Octave
****************************

   The procedure for installing Octave from source on a Unix-like
system is described below.  Building on other platforms will follow
similar steps.  Note that this description applies to Octave releases.
Building the development sources from the Mercurial archive requires
additional steps as described in *note Building the Development
Sources::.

* Menu:

* Build Dependencies::
* Running Configure and Make::
* Compiling Octave with 64-bit Indexing::
* Installation Problems::


File: octave.info,  Node: Build Dependencies,  Next: Running Configure and Make,  Up: Installation

G.1 Build Dependencies
======================

Octave is a fairly large program with many build dependencies.  You may
be able to find pre-packaged versions of the dependencies distributed as
part of your system, or you may have to build some or all of them
yourself.

* Menu:

* Obtaining the Depencies Automatically::
* Build Tools::
* External Packages::


File: octave.info,  Node: Obtaining the Depencies Automatically,  Next: Build Tools,  Up: Build Dependencies

G.1.1 Obtaining the Depencies Automatically
-------------------------------------------

On some systems you can obtain many of Octave's build dependencies
automatically. The commands for doing this vary by system. Similarly,
the names of pre-compiled packages vary by system and do not always
match exactly the names listed in *note Build Tools:: and *note
External Packages::.

   You will usually need the development version of an external
dependency so that you get the libraries and header files for building
software, not just for running already compiled programs.  These
packages typically have names that end with the suffix `-dev' or
`-devel'.

   On systems with `apt-get' (Debian, Ubuntu, etc.), you may be able to
install most of the tools and external packages using a command similar
to

     apt-get build-dep octave

The specific package name may be `octave3.2' or `octave3.4'.  The set
of required tools and external dependencies does not change frequently,
so it is not important that the version match exactly, but you should
use the most recent one available.

   On systems with `yum' (Fedora, Red Hat, etc.), you may be able to
install most of the tools and external packages using a command similar
to

     yum-builddep octave

The `yum-builddep' utility is part of the `yum-utils' package.

   For either type of system, the package name may include a version
number.  The set of required tools and external dependencies does not
change frequently, so it is not important that the version exactly match
the version you are installing, but you should use the most recent one
available.


File: octave.info,  Node: Build Tools,  Next: External Packages,  Prev: Obtaining the Depencies Automatically,  Up: Build Dependencies

G.1.2 Build Tools
-----------------

The following tools are required:

C++, C, and Fortran compilers
     The Octave sources are primarily written in C++, but some portions
     are also written in C and Fortran.  The Octave sources are
     intended to be portable.  Recent versions of the GNU compiler
     collection (GCC) should work (`http://gcc.gnu.org').  If you use
     GCC, you should avoid mixing versions.  For example, be sure that
     you are not using the obsolete `g77' Fortran compiler with modern
     versions of `gcc' and `g++'.

GNU Make
     Tool for building software (`http://www.gnu.org/software/make').
     Octave's build system requires GNU Make.  Other versions of Make
     will not work.  Fortunately, GNU Make is highly portable and easy
     to install.

AWK, sed, and other Unix utilities
     Basic Unix system utilities are required for building Octave.  All
     will be available with any modern Unix system and also on Windows
     with either Cygwin or MinGW and MSYS.

   Additionally, the following tools may be needed:

Bison
     Parser generator (`http://www.gnu.org/software/bison').  You will
     need Bison if you modify the `oct-parse.yy' source file or if you
     delete the files that are generated from it.

Flex
     Lexer analyzer (`http://www.gnu.org/software/flex').  You will need
     Flex if you modify the `lex.ll' source file or if you delete the
     files that are generated from it.

Autoconf
     Package for software configuration
     (`http://www.gnu.org/software/autoconf').  Autoconf is required if
     you modify Octave's `configure.ac' file or other files that it
     requires.

Automake
     Package for Makefile generation
     (`http://www.gnu.org/software/automake').  Automake is required if
     you modify Octave's `Makefile.am' files or other files that they
     depend on.

Libtool
     Package for building software libraries
     (`http://www.gnu.org/software/libtool').  Libtool is required by
     Automake.


File: octave.info,  Node: External Packages,  Prev: Build Tools,  Up: Build Dependencies

G.1.3 External Packages
-----------------------

The following external packages are required:

BLAS
     Basic Linear Algebra Subroutine library
     (`http://www.netlib.org/blas').  Accelerated BLAS libraries such as
     ATLAS (`http://math-atlas.sourceforge.net') are recommeded for
     better performance.

LAPACK
     Linear Algebra Package (`http://www.netlib.org/lapack').

PCRE
     The Perl Compatible Regular Expression library
     (http://www.pcre.org).

   The following external package is optional but strongly recommended:

GNU Readline
     Command-line editing library (`www.gnu.org/s/readline').

   If you wish to build Octave without GNU readline installed, you must
use the `--disable-readline' option when running the configure script.

   The following external software packages are optional but
recommended:

ARPACK
     Library for the solution of large-scale eigenvalue problems
     (`http://forge.scilab.org/index.php/p/arpack-ng').  ARPACK is
     required to provide the functions `eigs' and `svds'.

cURL
     Library for transferring data with URL syntax
     (`http://curl.haxx.se').  cURL is required to provide the
     `urlread' and `urlwrite' functions and the `ftp' class.

FFTW3
     Library for computing discrete Fourier transforms
     (`http://www.fftw.org').  FFTW3 is used to provide better
     performance for functions that compute discrete Fourier transforms
     (`fft', `ifft', `fft2', etc.)

FLTK
     Portable GUI toolkit (`http://www.fltk.org').  FLTK is currently
     used to provide windows for Octave's OpenGL-based graphics
     functions.

fontconfig
     Library for configuring and customizing font access
     (`http://www.freedesktop.org/wiki/Software/fontconfig').
     Fontconfig is used to manage fonts for Octave's OpenGL-based
     graphics functions.

FreeType
     Portable font engine (`http://www.freetype.org').  FreeType is used
     to perform font rendering for Octave's OpenGL-based graphics
     functions.

GLPK
     GNU Linear Programming Kit (`http://www.gnu.org/software/glpk').
     GPLK is required for the function `glpk'.

gnuplot
     Interactive graphics program (`http://www.gnuplot.info').  gnuplot
     is currently the default graphics renderer for Octave.

GraphicsMagick++
     Image processing library (`http://www.graphicsmagick.org').
     GraphicsMagick++ is used to provide the `imread' and `imwrite'
     functions.

HDF5
     Library for manipulating portable data files
     (`http://www.hdfgroup.org/HDF5').  HDF5 is required for Octave's
     `load' and `save' commands to read and write HDF data files.

OpenGL
     API for portable 2D and 3D graphics (`http://www.opengl.org').  An
     OpenGL implementation is required to provide Octave's OpenGL-based
     graphics functions.  Octave's OpenGL-based graphics functions
     usually outperform the gnuplot-based graphics functions because
     plot data can be rendered directly instead of sending data and
     commands to gnuplot for interpretation and rendering.

Qhull
     Computational geometry library (`http://www.qhull.org').  Qhull is
     required to provide the functions `convhull', `convhulln',
     `delaunay', `delaunay3', `delaunayn', `voronoi', and `voronoin'.

QRUPDATE
     QR factorization updating library
     (`http://sourceforge.net/projects/qrupdate').  QRUPDATE is used to
     provide improved performance for the functions `qrdelete',
     `qrinsert', `qrshift', and `qrupdate'.

SuiteSparse
     Sparse matrix factorization library
     (`http://www.cise.ufl.edu/research/sparse/SuiteSparse').
     SuiteSparse is required to provide sparse matrix factorizations and
     solution of linear equations for sparse systems.

zlib
     Data compression library (`http://zlib.net').  The zlib library is
     required for Octave's `load' and `save' commands to handle
     compressed data, including MATLAB v5 MAT files.


File: octave.info,  Node: Running Configure and Make,  Next: Compiling Octave with 64-bit Indexing,  Prev: Build Dependencies,  Up: Installation

G.2 Running Configure and Make
==============================

   * Run the shell script `configure'.  This will determine the features
     your system has (or doesn't have) and create a file named
     `Makefile' from each of the files named `Makefile.in'.

     Here is a summary of the configure options that are most
     frequently used when building Octave:

    `--help'
          Print a summary of the options recognized by the configure
          script.

    `--prefix=PREFIX'
          Install Octave in subdirectories below PREFIX.  The default
          value of PREFIX is `/usr/local'.

    `--srcdir=DIR'
          Look for Octave sources in the directory DIR.

    `--enable-64'
          This is an *experimental* option to enable Octave to use
          64-bit integers for array dimensions and indexing on 64-bit
          platforms.  You probably don't want to use this option unless
          you know what you are doing.  *Note Compiling Octave with
          64-bit Indexing::, for more details about building Octave
          with this option.

    `--enable-bounds-check'
          Enable bounds checking for indexing operators in the internal
          array classes.  This option is primarily used for debugging
          Octave.  Building Octave with this option has a negative
          impact on performance and is not recommended for general use.

    `--disable-docs'
          Disable building all forms of the documentation (Info, PDF,
          HTML).  The default is to build documentation, but your
          system will need functioning Texinfo and TeX installs for
          this to succeed.

    `--enable-float-truncate'
          This option allows for truncation of intermediate floating
          point results in calculations.  It is only necessary for
          certain platforms.

    `--enable-readline'
          Use the readline library to provide for editing of the
          command line in terminal environments.  This option is on by
          default.

    `--enable-shared'
          Create shared libraries (this is the default).  If you are
          planning to use the dynamic loading features, you will
          probably want to use this option.  It will make your `.oct'
          files much smaller and on some systems it may be necessary to
          build shared libraries in order to use dynamically linked
          functions.

          You may also want to build a shared version of `libstdc++',
          if your system doesn't already have one.

    `--enable-dl'
          Use `dlopen' and friends to make Octave capable of dynamically
          linking externally compiled functions (this is the default if
          `--enable-shared' is specified).  This option only works on
          systems that actually have these functions.  If you plan on
          using this feature, you should probably also use
          `--enable-shared' to reduce the size of your `.oct' files.

    `--with-blas=<lib>'
          By default, configure looks for the best BLAS matrix
          libraries on your system, including optimized implementations
          such as the free ATLAS 3.0, as well as vendor-tuned
          libraries.  (The use of an optimized BLAS will generally
          result in several-times faster matrix operations.)  Use this
          option to specify a particular BLAS library that Octave
          should use.

    `--with-lapack=<lib>'
          By default, configure looks for the best LAPACK matrix
          libraries on your system, including optimized implementations
          such as the free ATLAS 3.0, as well as vendor-tuned
          libraries.  (The use of an optimized LAPACK will generally
          result in several-times faster matrix operations.)  Use this
          option to specify a particular LAPACK library that Octave
          should use.

    `--with-magick=<lib>'
          Select the library to use for image I/O.  The two possible
          values are "GraphicsMagick" (default) or "ImageMagick".

    `--with-sepchar=<char>'
          Use <char> as the path separation character.  This option can
          help when running Octave on non-Unix systems.

    `--without-amd'
          Don't use AMD, disable some sparse matrix functionality.

    `--without-camd'
          Don't use CAMD, disable some sparse matrix functionality.

    `--without-colamd'
          Don't use COLAMD, disable some sparse matrix functionality.

    `--without-ccolamd'
          Don't use CCOLAMD, disable some sparse matrix functionality.

    `--without-cholmod'
          Don't use CHOLMOD, disable some sparse matrix functionality.

    `--without-curl'
          Don't use the cURL library, disable the ftp objects,
          `urlread' and `urlwrite' functions.

    `--without-cxsparse'
          Don't use CXSPARSE, disable some sparse matrix functionality.

    `--without-fftw3'
          Use the included FFTPACK library for computing Fast Fourier
          Transforms instead of the FFTW3 library.

    `--without-fftw3f'
          Use the included FFTPACK library for computing Fast Fourier
          Transforms instead of the FFTW3 library when operating on
          single precision (float) values.

    `--without-glpk'
          Don't use the GLPK library for linear programming.

    `--without-hdf5'
          Don't use the HDF5 library, disable reading and writing of
          HDF5 files.

    `--without-opengl'
          Don't use OpenGL, disable native graphics toolkit for
          plotting.  You will need `gnuplot' installed in order to make
          plots.

    `--without-qhull'
          Don't use Qhull, disable `delaunay', `convhull', and related
          functions.

    `--without-qrupdate'
          Don't use QRUPDATE, disable QR and Cholesky update functions.

    `--without-umfpack'
          Don't use UMFPACK, disable some sparse matrix functionality.

    `--without-zlib'
          Don't use the zlib library, disable data file compression and
          support for recent MAT file formats.

    `--without-framework-carbon'
          Don't use framework Carbon headers, libraries, or specific
          source code even if the configure test succeeds (the default
          is to use Carbon framework if available).  This is a platform
          specific configure option for Mac systems.

    `--without-framework-opengl'
          Don't use framework OpenGL headers, libraries, or specific
          source code even if the configure test succeeds.  If this
          option is given then OpenGL headers and libraries in standard
          system locations are tested (the default value is
          `--with-framework-opengl').  This is a platform specific
          configure option for Mac systems.


     See the file `INSTALL' for more general information about the
     command line options used by configure.  That file also contains
     instructions for compiling in a directory other than the one where
     the source is located.

   * Run make.

     You will need a recent version of GNU Make as Octave relies on
     certain features not generally available in all versions of make.
     Modifying Octave's makefiles to work with other make programs is
     probably not worth your time; instead, we simply recommend
     installing GNU Make.

     There are currently two options for plotting in Octave: (1) the
     external program gnuplot, or (2) the internal graphics engine
     using OpenGL and FLTK.  Gnuplot is a command-driven interactive
     function plotting program.  Gnuplot is copyrighted, but freely
     distributable.  As of Octave release 3.4, gnuplot is the default
     option for plotting.  But, the internal graphics engine is nearly
     100% compatible, certainly for most ordinary plots, and users are
     encouraged to test it.  It is anticipated that the internal engine
     will become the default option at the next major release of Octave.

     To compile Octave, you will need a recent version of `g++' or other
     ANSI C++ compiler.  In addition, you will need a Fortran 77
     compiler or `f2c'.  If you use `f2c', you will need a script like
     `fort77' that works like a normal Fortran compiler by combining
     `f2c' with your C compiler in a single script.

     If you plan to modify the parser you will also need GNU `bison' and
     `flex'.  If you modify the documentation, you will need GNU
     Texinfo.

     GNU Make, `gcc' (and `libstdc++'), `gnuplot', `bison', `flex', and
     Texinfo are all available from many anonymous ftp archives.  The
     primary site is `ftp.gnu.org', but it is often very busy.  A list
     of sites that mirror the software on `ftp.gnu.org' is available by
     anonymous ftp from `ftp://ftp.gnu.org/pub/gnu/GNUinfo/FTP'.

     Octave requires approximately 1.4 GB of disk storage to unpack and
     compile from source (significantly less, 400 MB, if you don't
     compile with debugging symbols).  To compile without debugging
     symbols try the command

          make CFLAGS=-O CXXFLAGS=-O LDFLAGS=

     instead of just `make'.

   * If you encounter errors while compiling Octave, first check the
     list of known problems below to see if there is a workaround or
     solution for your problem.  If not, see *note Trouble::, for
     information about how to report bugs.

   * Once you have successfully compiled Octave, run `make install'.

     This will install a copy of Octave, its libraries, and its
     documentation in the destination directory.  As distributed,
     Octave is installed in the following directories.  In the table
     below, PREFIX defaults to `/usr/local', VERSION stands for the
     current version number of the interpreter, and ARCH is the type of
     computer on which Octave is installed (for example,
     `i586-unknown-gnu').

    `PREFIX/bin'
          Octave and other binaries that people will want to run
          directly.

    `PREFIX/lib/octave-VERSION'
          Libraries like libcruft.a and liboctave.a.

    `PREFIX/octave-VERSION/include/octave'
          Include files distributed with Octave.

    `PREFIX/share'
          Architecture-independent data files.

    `PREFIX/share/man/man1'
          Unix-style man pages describing Octave.

    `PREFIX/share/info'
          Info files describing Octave.

    `PREFIX/share/octave/VERSION/m'
          Function files distributed with Octave.  This includes the
          Octave version, so that multiple versions of Octave may be
          installed at the same time.

    `PREFIX/libexec/octave/VERSION/exec/ARCH'
          Executables to be run by Octave rather than the user.

    `PREFIX/lib/octave/VERSION/oct/ARCH'
          Object files that will be dynamically loaded.

    `PREFIX/share/octave/VERSION/imagelib'
          Image files that are distributed with Octave.


File: octave.info,  Node: Compiling Octave with 64-bit Indexing,  Next: Installation Problems,  Prev: Running Configure and Make,  Up: Installation

G.3 Compiling Octave with 64-bit Indexing
=========================================

Note: the following only applies to systems that have 64-bit pointers.
Configuring Octave with `--enable-64' cannot magically make a 32-bit
system have a 64-bit address space.

   On 64-bit systems, Octave is limited to (approximately) the following
array sizes when using the default 32-bit indexing mode:

     double:         16GB
     single:          8GB
     uint64, int64:  16GB
     uint32, int32:   8GB
     uint16, int16:   4GB
     uint8, int8:     2GB

   In each case, the limit is really (approximately) 2^31 elements
because of the default type of the value used for indexing arrays
(signed 32-bit integer, corresponding to the size of a Fortran INTEGER
value).

   Trying to create larger arrays will produce the following error:

     octave:1> a = zeros (1024*1024*1024*3, 1, 'int8');
     error: memory exhausted or requested size too large
            for range of Octave's index type --
            trying to return to prompt

You will obtain this error even if your system has enough memory to
create this array (4 GB in the above case).

   To use arrays larger than 2 GB, Octave has to be configured with the
option `--enable-64'.  This option is experimental and you are
encouraged to submit bug reports if you find a problem.  With this
option, Octave will use 64-bit integers internally for array dimensions
and indexing.  However, all numerical libraries used by Octave will
*also* need to use 64-bit integers for array dimensions and indexing.
In most cases, this means they will need to be compiled from source
since most (all?) distributions which package these libraries compile
them with the default Fortran integer size, which is normally 32-bits
wide.

   The following instructions were tested with the development version
of Octave and GCC 4.3.4 on an x86_64 Debian system.

   The versions listed below are the versions used for testing.  If
newer versions of these packages are available, you should try to use
them, although there may be some differences.

   All libraries and header files will be installed in subdirectories of
`$prefix64' (you must choose the location of this directory).

   * BLAS and LAPACK (`http://www.netlib.org/lapack')

     Reference versions for both libraries are included in the reference
     LAPACK 3.2.1 distribution from `netlib.org'.

        - Copy the file `make.inc.example' and name it `make.inc'.  The
          options `-fdefault-integer-8' and `-fPIC' (on 64-bit CPU)
          have to be added to the variable `OPTS' and `NOOPT'.

        - Once you have compiled this library make sure that you use it
          for compiling Suite Sparse and Octave.  In the following we
          assume that you installed the LAPACK library as
          $prefix64/lib/liblapack.a.

   * QRUPDATE (`http://sourceforge.net/projects/qrupdate')

     In the `Makeconf' file:

        - Add `-fdefault-integer-8' to `FFLAGS'.

        - Adjust the BLAS and LAPACK variables as needed if your 64-bit
          aware BLAS and LAPACK libraries are in a non-standard
          location.

        - Set `PREFIX' to the top-level directory of your install tree.

        - Run `make solib' to make a shared library.

        - Run `make install' to install the library.

   * SuiteSparse (`http://www.cise.ufl.edu/research/sparse/SuiteSparse')

        - In `UFconfig/UFconfig.mk' use the following options for
          `CFLAGS' and `F77FLAGS':

               CC = gcc
               CFLAGS = -fPIC -O -DLP64 -DLONGBLAS='long int' -DLONG='long int'
               F77 = gfortran
               F77FLAGS = -fPIC -O -fdefault-integer-8
               BLAS = -L$BLAS/lib -lblas -lgfortran"
               LAPACK = -L$LAPACK/lib -llapack"

        - Disable the GPL-incompatible `METIS' library:

               CHOLMOD_CONFIG = -DNPARTITION
               SPQR_CONFIG = -DNPARTITION
               METIS_PATH =
               METIS =

        - Disable the `DI' versions of the `CHOLMOD' library files by
          setting

               OBJ = $(DL)

          in `CHOLMOD/Lib/Makefile'.

        - Disable the `DI' versions of the `CHOLMOD' tests by commenting
          out or deleting the following lines in
          `CHOLMOD/Demo/Makefile':

               ./cholmod_demo < Matrix/bcsstk01.tri
               ./cholmod_demo < Matrix/lp_afiro.tri
               ./cholmod_demo < Matrix/can___24.mtx
               ./cholmod_demo < Matrix/c.tri
               ./cholmod_simple < Matrix/c.tri
               ./cholmod_simple < Matrix/can___24.mtx
               ./cholmod_simple < Matrix/bcsstk01.tri

        - Run `make' to build the libraries.

        - The SuiteSparse `Makefile' does not have an install target so
          you must install the files by hand:

               mkdir $prefix64/include/suitesparse
               cp UFconfig/UFconfig.h $prefix64/include/suitesparse
               for d in AMD BTF CAMD CCOLAMD \
                        CHOLMOD COLAMD CXSparse UMFPACK; do
                 cp $d/Lib/lib*a $prefix64/lib
                 cp $d/Include/*h $prefix64/include/suitesparse
               done

        - You can generate shared versions of these libraries by doing
          the following in the `$prefix64/lib' directory:

               top=$(pwd)
               for f in *.a; do
                 mkdir tmp
                 cd tmp
                 ar vx ../$f
                 gcc -shared -o ../${f%%.a}.so *.o
                 cd $top
                 rm -rf tmp
               done


   * ATLAS instead of reference BLAS and LAPACK

     Suggestions on how to compile ATLAS would be most welcome.

   * GLPK

     Suggestions on how to compile GLPK would be most welcome.

   * Qhull (`http://www.qhull.org')

     Suggestions on how to compile Qhull would be most welcome.

   * Octave

     Octave's 64-bit index support is activated with the configure
     option `--enable-64'.

          ./configure \
            LD_LIBRARY_PATH="$prefix64/lib" \
            CPPFLAGS="-I$prefix64/include" LDFLAGS="-L$prefix64/lib" \
            --enable-64

     You must ensure that all Fortran sources except those in the
     `libcruft/ranlib' directory are compiled such that INTEGERS are
     8-bytes wide.  If you are using gfortan, the configure script
     should automatically set the Makefile variable
     `F77_INTEGER_8_FLAG' to `-fdefault-integer-8'.  If you are using
     another compiler, you must set this variable yourself.  You should
     NOT set this flag in `FFLAGS', otherwise the files in
     `libcruft/ranlib' will be miscompiled.

   * Other dependencies

     Probably nothing special needs to be done for the following
     dependencies.  If you discover that something does need to be done,
     please submit a bug report.

        - pcre

        - zlib

        - hdf5

        - fftw3

        - cURL

        - GraphicsMagick++

        - OpenGL

        - freetype

        - fontconfig

        - fltk



File: octave.info,  Node: Installation Problems,  Prev: Compiling Octave with 64-bit Indexing,  Up: Installation

G.4 Installation Problems
=========================

This section contains a list of problems (and some apparent problems
that don't really mean anything is wrong) that may show up during
installation of Octave.

   * On some SCO systems, `info' fails to compile if `HAVE_TERMIOS_H'
     is defined in `config.h'.  Simply removing the definition from
     `info/config.h' should allow it to compile.

   * If `configure' finds `dlopen', `dlsym', `dlclose', and `dlerror',
     but not the header file `dlfcn.h', you need to find the source for
     the header file and install it in the directory `usr/include'.
     This is reportedly a problem with Slackware 3.1.  For Linux/GNU
     systems, the source for `dlfcn.h' is in the `ldso' package.

   * Building `.oct' files doesn't work.

     You should probably have a shared version of `libstdc++'.  A patch
     is needed to build shared versions of version 2.7.2 of `libstdc++'
     on the HP-PA architecture.  You can find the patch at
     `ftp://ftp.cygnus.com/pub/g++/libg++-2.7.2-hppa-gcc-fix'.

   * On some DEC alpha systems there may be a problem with the `libdxml'
     library, resulting in floating point errors and/or segmentation
     faults in the linear algebra routines called by Octave.  If you
     encounter such problems, then you should modify the configure
     script so that `SPECIAL_MATH_LIB' is not set to `-ldxml'.

   * On FreeBSD systems Octave may hang while initializing some internal
     constants.  The fix appears to be to use

          options      GPL_MATH_EMULATE

     rather than

          options      MATH_EMULATE

     in the kernel configuration files (typically found in the directory
     `/sys/i386/conf'.  After making this change, you'll need to rebuild
     the kernel, install it, and reboot.

   * If you encounter errors like

          passing `void (*)()' as argument 2 of
            `octave_set_signal_handler(int, void (*)(int))'

     or

          warning: ANSI C++ prohibits conversion from `(int)'
                   to `(...)'

     while compiling `sighandlers.cc', you may need to edit some files
     in the `gcc' include subdirectory to add proper prototypes for
     functions there.  For example, Ultrix 4.2 needs proper
     declarations for the `signal' function and the `SIG_IGN' macro in
     the file `signal.h'.

     On some systems the `SIG_IGN' macro is defined to be something
     like this:

          #define  SIG_IGN  (void (*)())1

     when it should really be something like:

          #define  SIG_IGN  (void (*)(int))1

     to match the prototype declaration for the `signal' function.  This
     change should also be made for the `SIG_DFL' and `SIG_ERR'
     symbols.  It may be necessary to change the definitions in
     `sys/signal.h' as well.

     The `gcc' `fixincludes' and `fixproto' scripts should probably fix
     these problems when `gcc' installs its modified set of header
     files, but I don't think that's been done yet.

     *You should not change the files in `/usr/include'*.  You can find
     the `gcc' include directory tree by running the command

          gcc -print-libgcc-file-name

     The directory of `gcc' include files normally begins in the same
     directory that contains the file `libgcc.a'.

   * Some of the Fortran subroutines may fail to compile with older
     versions of the Sun Fortran compiler.  If you get errors like

          zgemm.f:
                  zgemm:
          warning: unexpected parent of complex expression subtree
          zgemm.f, line 245: warning: unexpected parent of complex
            expression subtree
          warning: unexpected parent of complex expression subtree
          zgemm.f, line 304: warning: unexpected parent of complex
            expression subtree
          warning: unexpected parent of complex expression subtree
          zgemm.f, line 327: warning: unexpected parent of complex
            expression subtree
          pcc_binval: missing IR_CONV in complex op
          make[2]: *** [zgemm.o] Error 1

     when compiling the Fortran subroutines in the `libcruft'
     subdirectory, you should either upgrade your compiler or try
     compiling with optimization turned off.

   * On NeXT systems, if you get errors like this:

          /usr/tmp/cc007458.s:unknown:Undefined local
                symbol LBB7656
          /usr/tmp/cc007458.s:unknown:Undefined local
                symbol LBE7656

     when compiling `Array.cc' and `Matrix.cc', try recompiling these
     files without `-g'.

   * Some people have reported that calls to system() and the pager do
     not work on SunOS systems.  This is apparently due to having
     `G_HAVE_SYS_WAIT' defined to be 0 instead of 1 when compiling
     `libg++'.

   * On NeXT systems, linking to `libsys_s.a' may fail to resolve the
     following functions

          _tcgetattr
          _tcsetattr
          _tcflow

     which are part of `libposix.a'.  Unfortunately, linking Octave with
     `-posix' results in the following undefined symbols.

          .destructors_used
          .constructors_used
          _objc_msgSend
          _NXGetDefaultValue
          _NXRegisterDefaults
          .objc_class_name_NXStringTable
          .objc_class_name_NXBundle

     One kluge around this problem is to extract `termios.o' from
     `libposix.a', put it in Octave's `src' directory, and add it to
     the list of files to link together in the makefile.  Suggestions
     for better ways to solve this problem are welcome!

   * If Octave crashes immediately with a floating point exception, it
     is likely that it is failing to initialize the IEEE floating point
     values for infinity and NaN.

     If your system actually does support IEEE arithmetic, you should
     be able to fix this problem by modifying the function
     `octave_ieee_init' in the file `lo-ieee.cc' to correctly
     initialize Octave's internal infinity and NaN variables.

     If your system does not support IEEE arithmetic but Octave's
     configure script incorrectly determined that it does, you can work
     around the problem by editing the file `config.h' to not define
     `HAVE_ISINF', `HAVE_FINITE', and `HAVE_ISNAN'.

     In any case, please report this as a bug since it might be
     possible to modify Octave's configuration script to automatically
     determine the proper thing to do.

   * If Octave is unable to find a header file because it is installed
     in a location that is not normally searched by the compiler, you
     can add the directory to the include search path by specifying
     (for example) `CPPFLAGS=-I/some/nonstandard/directory' as an
     argument to `configure'.  Other variables that can be specified
     this way are `CFLAGS', `CXXFLAGS', `FFLAGS', and `LDFLAGS'.
     Passing them as options to the configure script also records them
     in the `config.status' file.  By default, `CPPFLAGS' and `LDFLAGS'
     are empty, `CFLAGS' and `CXXFLAGS' are set to `"-g -O"' and
     `FFLAGS' is set to `"-O"'.



File: octave.info,  Node: Emacs Octave Support,  Next: Grammar and Parser,  Prev: Installation,  Up: Top

Appendix H Emacs Octave Support
*******************************

The development of Octave code can greatly be facilitated using Emacs
with Octave mode, a major mode for editing Octave files which can e.g.
automatically indent the code, do some of the typing (with Abbrev mode)
and show keywords, comments, strings, etc. in different faces (with
Font-lock mode on devices that support it).

   It is also possible to run Octave from within Emacs, either by
directly entering commands at the prompt in a buffer in Inferior Octave
mode, or by interacting with Octave from within a file with Octave
code.  This is useful in particular for debugging Octave code.

   Finally, you can convince Octave to use the Emacs info reader for
`help -i'.

   All functionality is provided by the Emacs Lisp package EOS (for
"Emacs Octave Support").  This chapter describes how to set up and use
this package.

   Please contact <Kurt.Hornik@wu-wien.ac.at> if you have any questions
or suggestions on using EOS.

* Menu:

* Installing EOS::
* Using Octave Mode::
* Running Octave from Within Emacs::
* Using the Emacs Info Reader for Octave::


File: octave.info,  Node: Installing EOS,  Next: Using Octave Mode,  Up: Emacs Octave Support

H.1 Installing EOS
==================

The Emacs package EOS consists of the three files `octave-mod.el',
`octave-inf.el', and `octave-hlp.el'.  These files, or better yet their
byte-compiled versions, should be somewhere in your Emacs load-path.

   If you have GNU Emacs with a version number at least as high as
19.35, you are all set up, because EOS is respectively will be part of
GNU Emacs as of version 19.35.

   Otherwise, copy the three files from the `emacs' subdirectory of the
Octave distribution to a place where Emacs can find them (this depends
on how your Emacs was installed).  Byte-compile them for speed if you
want.


File: octave.info,  Node: Using Octave Mode,  Next: Running Octave from Within Emacs,  Prev: Installing EOS,  Up: Emacs Octave Support

H.2 Using Octave Mode
=====================

If you are lucky, your sysadmins have already arranged everything so
that Emacs automatically goes into Octave mode whenever you visit an
Octave code file as characterized by its extension `.m'.  If not,
proceed as follows.

  1. To begin using Octave mode for all `.m' files you visit, add the
     following lines to a file loaded by Emacs at startup time,
     typically your `~/.emacs' file:

          (autoload 'octave-mode "octave-mod" nil t)
          (setq auto-mode-alist
                (cons '("\\.m$" . octave-mode) auto-mode-alist))

  2. Finally, to turn on the abbrevs, auto-fill and font-lock features
     automatically, also add the following lines to one of the Emacs
     startup files:
          (add-hook 'octave-mode-hook
                    (lambda ()
                      (abbrev-mode 1)
                      (auto-fill-mode 1)
                      (if (eq window-system 'x)
                          (font-lock-mode 1))))
     See the Emacs manual for more information about how to customize
     Font-lock mode.

   In Octave mode, the following special Emacs commands can be used in
addition to the standard Emacs commands.

`C-h m'
     Describe the features of Octave mode.

`LFD'
     Reindent the current Octave line, insert a newline and indent the
     new line (`octave-reindent-then-newline-and-indent').  An abbrev
     before point is expanded if `abbrev-mode' is non-`nil'.

`TAB'
     Indents current Octave line based on its contents and on previous
     lines (`indent-according-to-mode').

`;'
     Insert an "electric" semicolon (`octave-electric-semi').  If
     `octave-auto-indent' is non-`nil', reindent the current line.  If
     `octave-auto-newline' is non-`nil', automagically insert a newline
     and indent the new line.

``'
     Start entering an abbreviation (`octave-abbrev-start').  If Abbrev
     mode is turned on, typing ``C-h' or ``?' lists all abbrevs.  Any
     other key combination is executed normally.  Note that all Octave
     abbrevs start with a grave accent.

`M-LFD'
     Break line at point and insert continuation marker and alignment
     (`octave-split-line').

`M-TAB'
     Perform completion on Octave symbol preceding point, comparing that
     symbol against Octave's reserved words and built-in variables
     (`octave-complete-symbol').

`M-C-a'
     Move backward to the beginning of a function
     (`octave-beginning-of-defun').  With prefix argument N, do it that
     many times if N is positive; otherwise, move forward to the N-th
     following beginning of a function.

`M-C-e'
     Move forward to the end of a function (`octave-end-of-defun').
     With prefix argument N, do it that many times if N is positive;
     otherwise, move back to the N-th preceding end of a function.

`M-C-h'
     Puts point at beginning and mark at the end of the current Octave
     function, i.e., the one containing point or following point
     (`octave-mark-defun').

`M-C-q'
     Properly indents the Octave function which contains point
     (`octave-indent-defun').

`M-;'
     If there is no comment already on this line, create a code-level
     comment (started by two comment characters) if the line is empty,
     or an in-line comment (started by one comment character) otherwise
     (`octave-indent-for-comment').  Point is left after the start of
     the comment which is properly aligned.

`C-c ;'
     Puts the comment character `#' (more precisely, the string value of
     `octave-comment-start') at the beginning of every line in the
     region (`octave-comment-region').  With just `C-u' prefix
     argument, uncomment each line in the region.  A numeric prefix
     argument N means use N comment characters.

`C-c :'
     Uncomments every line in the region (`octave-uncomment-region').

`C-c C-p'
     Move one line of Octave code backward, skipping empty and comment
     lines (`octave-previous-code-line').  With numeric prefix argument
     N, move that many code lines backward (forward if N is negative).

`C-c C-n'
     Move one line of Octave code forward, skipping empty and comment
     lines (`octave-next-code-line').  With numeric prefix argument N,
     move that many code lines forward (backward if N is negative).

`C-c C-a'
     Move to the `real' beginning of the current line
     (`octave-beginning-of-line').  If point is in an empty or comment
     line, simply go to its beginning; otherwise, move backwards to the
     beginning of the first code line which is not inside a continuation
     statement, i.e., which does not follow a code line ending in `...'
     or `\', or is inside an open parenthesis list.

`C-c C-e'
     Move to the `real' end of the current line (`octave-end-of-line').
     If point is in a code line, move forward to the end of the first
     Octave code line which does not end in `...' or `\' or is inside an
     open parenthesis list.  Otherwise, simply go to the end of the
     current line.

`C-c M-C-n'
     Move forward across one balanced begin-end block of Octave code
     (`octave-forward-block').  With numeric prefix argument N, move
     forward across N such blocks (backward if N is negative).

`C-c M-C-p'
     Move back across one balanced begin-end block of Octave code
     (`octave-backward-block').  With numeric prefix argument N, move
     backward across N such blocks (forward if N is negative).

`C-c M-C-d'
     Move forward down one begin-end block level of Octave code
     (`octave-down-block').  With numeric prefix argument, do it that
     many times; a negative argument means move backward, but still go
     down one level.

`C-c M-C-u'
     Move backward out of one begin-end block level of Octave code
     (`octave-backward-up-block').  With numeric prefix argument, do it
     that many times; a negative argument means move forward, but still
     to a less deep spot.

`C-c M-C-h'
     Put point at the beginning of this block, mark at the end
     (`octave-mark-block').  The block marked is the one that contains
     point or follows point.

`C-c ]'
     Close the current block on a separate line (`octave-close-block').
     An error is signaled if no block to close is found.

`C-c f'
     Insert a function skeleton, prompting for the function's name,
     arguments and return values which have to be entered without
     parentheses (`octave-insert-defun').

`C-c C-h'
     Search the function, operator and variable indices of all info
     files with documentation for Octave for entries (`octave-help').
     If used interactively, the entry is prompted for with completion.
     If multiple matches are found, one can cycle through them using
     the standard `,' (`Info-index-next') command of the Info reader.

     The variable `octave-help-files' is a list of files to search
     through and defaults to `'("octave")'.  If there is also an Octave
     Local Guide with corresponding info file, say, `octave-LG', you can
     have `octave-help' search both files by
          (setq octave-help-files '("octave" "octave-LG"))
     in one of your Emacs startup files.


   A common problem is that the <RET> key does _not_ indent the line to
where the new text should go after inserting the newline.  This is
because the standard Emacs convention is that <RET> (aka `C-m') just
adds a newline, whereas <LFD> (aka `C-j') adds a newline and indents
it.  This is particularly inconvenient for users with keyboards which
do not have a special <LFD> key at all; in such cases, it is typically
more convenient to use <RET> as the <LFD> key (rather than typing
`C-j').

   You can make <RET> do this by adding
     (define-key octave-mode-map "\C-m"
       'octave-reindent-then-newline-and-indent)
   to one of your Emacs startup files.  Another, more generally
applicable solution is
     (defun RET-behaves-as-LFD ()
       (let ((x (key-binding "\C-j")))
         (local-set-key "\C-m" x)))
     (add-hook 'octave-mode-hook 'RET-behaves-as-LFD)
   (this works for all modes by adding to the startup hooks, without
having to know the particular binding of <RET> in that mode!).  Similar
considerations apply for using <M-RET> as <M-LFD>.  As Barry A. Warsaw
<bwarsaw@cnri.reston.va.us> says in the documentation for his
`cc-mode', "This is a very common question.  `:-)' If you want this to
be the default behavior, don't lobby me, lobby RMS!"

   The following variables can be used to customize Octave mode.

`octave-auto-indent'
     Non-`nil' means auto-indent the current line after a semicolon or
     space.  Default is `nil'.

`octave-auto-newline'
     Non-`nil' means auto-insert a newline and indent after semicolons
     are typed.  The default value is `nil'.

`octave-blink-matching-block'
     Non-`nil' means show matching begin of block when inserting a
     space, newline or `;' after an else or end keyword.  Default is
     `t'.  This is an extremely useful feature for automatically
     verifying that the keywords match--if they don't, an error message
     is displayed.

`octave-block-offset'
     Extra indentation applied to statements in block structures.
     Default is 2.

`octave-continuation-offset'
     Extra indentation applied to Octave continuation lines.  Default
     is 4.

`octave-continuation-string'
     String used for Octave continuation lines.  Normally `\'.

`octave-mode-startup-message'
     If `t' (default), a startup message is displayed when Octave mode
     is called.


   If Font Lock mode is enabled, Octave mode will display
   * strings in `font-lock-string-face'

   * comments in `font-lock-comment-face'

   * the Octave reserved words (such as all block keywords) and the text
     functions (such as `cd' or `who') which are also reserved using
     `font-lock-keyword-face'

   * the built-in operators (`&&', `==', ...) using
     `font-lock-reference-face'

   * and the function names in function declarations in
     `font-lock-function-name-face'.

   There is also rudimentary support for Imenu (currently, function
names can be indexed).

   You can generate TAGS files for Emacs from Octave `.m' files using
the shell script `octave-tags' that is installed alongside your copy of
Octave.

   Customization of Octave mode can be performed by modification of the
variable `octave-mode-hook'.  If the value of this variable is
non-`nil', turning on Octave mode calls its value.

   If you discover a problem with Octave mode, you can conveniently
send a bug report using `C-c C-b' (`octave-submit-bug-report').  This
automatically sets up a mail buffer with version information already
added.  You just need to add a description of the problem, including a
reproducible test case and send the message.


File: octave.info,  Node: Running Octave from Within Emacs,  Next: Using the Emacs Info Reader for Octave,  Prev: Using Octave Mode,  Up: Emacs Octave Support

H.3 Running Octave from Within Emacs
====================================

The package `octave' provides commands for running an inferior Octave
process in a special Emacs buffer.  Use
     M-x run-octave
   to directly start an inferior Octave process.  If Emacs does not know
about this command, add the line
     (autoload 'run-octave "octave-inf" nil t)
   to your `.emacs' file.

   This will start Octave in a special buffer the name of which is
specified by the variable `inferior-octave-buffer' and defaults to
`"*Inferior Octave*"'.  From within this buffer, you can interact with
the inferior Octave process `as usual', i.e., by entering Octave
commands at the prompt.  The buffer is in Inferior Octave mode, which
is derived from the standard Comint mode, a major mode for interacting
with an inferior interpreter.  See the documentation for `comint-mode'
for more details, and use `C-h b' to find out about available special
keybindings.

   You can also communicate with an inferior Octave process from within
files with Octave code (i.e., buffers in Octave mode), using the
following commands.

`C-c i l'
     Send the current line to the inferior Octave process
     (`octave-send-line').  With positive prefix argument N, send that
     many lines.  If `octave-send-line-auto-forward' is non-`nil', go
     to the next unsent code line.

`C-c i b'
     Send the current block to the inferior Octave process
     (`octave-send-block').

`C-c i f'
     Send the current function to the inferior Octave process
     (`octave-send-defun').

`C-c i r'
     Send the region to the inferior Octave process
     (`octave-send-region').

`C-c i s'
     Make sure that `inferior-octave-buffer' is displayed
     (`octave-show-process-buffer').

`C-c i h'
     Delete all windows that display the inferior Octave buffer
     (`octave-hide-process-buffer').

`C-c i k'
     Kill the inferior Octave process and its buffer
     (`octave-kill-process').

   The effect of the commands which send code to the Octave process can
be customized by the following variables.
`octave-send-echo-input'
     Non-`nil' means echo input sent to the inferior Octave process.
     Default is `t'.

`octave-send-show-buffer'
     Non-`nil' means display the buffer running the Octave process after
     sending a command (but without selecting it).  Default is `t'.

   If you send code and there is no inferior Octave process yet, it
will be started automatically.

   The startup of the inferior Octave process is highly customizable.
The variable `inferior-octave-startup-args' can be used for specifying
command lines arguments to be passed to Octave on startup as a list of
strings.  For example, to suppress the startup message and use
`traditional' mode, set this to `'("-q" "--traditional")'.  You can
also specify a startup file of Octave commands to be loaded on startup;
note that these commands will not produce any visible output in the
process buffer.  Which file to use is controlled by the variable
`inferior-octave-startup-file'.  If this is `nil', the file
`~/.emacs-octave' is used if it exists.

   And finally, `inferior-octave-mode-hook' is run after starting the
process and putting its buffer into Inferior Octave mode.  Hence, if you
like the up and down arrow keys to behave in the interaction buffer as
in the shell, and you want this buffer to use nice colors, add
     (add-hook 'inferior-octave-mode-hook
               (lambda ()
                 (turn-on-font-lock)
                 (define-key inferior-octave-mode-map [up]
                   'comint-previous-input)
                 (define-key inferior-octave-mode-map [down]
                   'comint-next-input)))
   to your `.emacs' file.  You could also swap the roles of `C-a'
(`beginning-of-line') and `C-c C-a' (`comint-bol') using this hook.

     *Note* that if you set your Octave prompts to something different
     from the defaults, make sure that `inferior-octave-prompt' matches
     them.  Otherwise, _nothing_ will work, because Emacs will not know
     when Octave is waiting for input, or done sending output.


File: octave.info,  Node: Using the Emacs Info Reader for Octave,  Prev: Running Octave from Within Emacs,  Up: Emacs Octave Support

H.4 Using the Emacs Info Reader for Octave
==========================================

You may also use the Emacs Info reader with Octave's `doc' function.
For this, the package `gnuserv' needs to be installed.

   If `gnuserv' is installed, add the lines
     (autoload 'octave-help "octave-hlp" nil t)
     (require 'gnuserv)
     (gnuserv-start)
   to your `.emacs' file.

   You can use either `plain' Emacs Info or the function `octave-help'
as your Octave info reader (for `help -i').  In the former case, use
`info_program ("info-emacs-info")'.  The latter is perhaps more
attractive because it allows to look up keys in the indices of
_several_ info files related to Octave (provided that the Emacs
variable `octave-help-files' is set correctly).  In this case, use
`info_program ("info-emacs-octave-help")'.

   If you use Octave from within Emacs, it is best to add these
settings to your `~/.emacs-octave' startup file (or the file pointed to
by the Emacs variable `inferior-octave-startup-file').


File: octave.info,  Node: Grammar and Parser,  Next: Copying,  Prev: Emacs Octave Support,  Up: Top

Appendix I Grammar and Parser
*****************************

This appendix will eventually contain a semi-formal description of
Octave's language.

* Menu:

* Keywords::
* Parser::


File: octave.info,  Node: Keywords,  Next: Parser,  Up: Grammar and Parser

I.1 Keywords
============

The following identifiers are keywords, and may not be used as variable
or function names:

`__FILE__'               `__LINE__'               `break'
`case'                   `catch'                  `classdef'
`continue'               `do'                     `else'
`elseif'                 `end'                    `end_try_catch'
`end_unwind_protect'     `endclassdef'            `endenumeration'
`endevents'              `endfor'                 `endfunction'
`endif'                  `endmethods'             `endparfor'
`endproperties'          `endswitch'              `endwhile'
`enumeration'            `events'                 `for'
`function'               `get'                    `global'
`if'                     `methods'                `otherwise'
`parfor'                 `persistent'             `properties'
`return'                 `set'                    `static'
`switch'                 `try'                    `until'
`unwind_protect'         `unwind_protect_cleanup' `while'

   The function `iskeyword' can be used to quickly check whether an
identifier is reserved by Octave.

 -- Built-in Function:  iskeyword ()
 -- Built-in Function:  iskeyword (NAME)
     Return true if NAME is an Octave keyword.  If NAME is omitted,
     return a list of keywords.

     *See also:* *note isvarname: doc-isvarname, *note exist: doc-exist.


File: octave.info,  Node: Parser,  Prev: Keywords,  Up: Grammar and Parser

I.2 Parser
==========

The parser has a number of variables that affect its internal operation.
These variables are generally documented in the manual alongside the
code that they affect.  For example, `allow_noninteger_range_as_index'
is discussed in the section on index expressions.

   In addition, there are three non-specific parser customization
functions.  `add_input_event_hook' can be used to schedule a user
function for periodic evaluation.  `remove_input_event_hook' will stop
a user function from being evaluated periodically.

 -- Built-in Function:  add_input_event_hook (FCN)
 -- Built-in Function:  add_input_event_hook (FCN, DATA)
     Add the named function FCN to the list of functions to call
     periodically when Octave is waiting for input.  The function should
     have the form

          FCN (DATA)

     If DATA is omitted, Octave calls the function without any
     arguments.

     *See also:* *note remove_input_event_hook:
     doc-remove_input_event_hook.

 -- Built-in Function:  remove_input_event_hook (FCN)
     Remove the named function FCN from the list of functions to call
     periodically when Octave is waiting for input.

     *See also:* *note add_input_event_hook: doc-add_input_event_hook.

   Finally, when the parser cannot identify an input token it calls a
particular function to handle this.  By default, this is the function
"unimplemented" which makes suggestions about possible Octave
substitutes for MATLAB functions.

 -- Built-in Function: VAL = missing_function_hook ()
 -- Built-in Function: OLD_VAL = missing_function_hook (NEW_VAL)
 -- Built-in Function:  missing_function_hook (NEW_VAL, "local")
     Query or set the internal variable that specifies the function to
     call when an unknown identifier is requested.

     When called from inside a function with the "local" option, the
     variable is changed locally for the function and any subroutines
     it calls.  The original variable value is restored when exiting
     the function.


File: octave.info,  Node: Copying,  Next: Concept Index,  Prev: Grammar and Parser,  Up: Top

Appendix J GNU GENERAL PUBLIC LICENSE
*************************************

                        Version 3, 29 June 2007

     Copyright (C) 2007 Free Software Foundation, Inc. `http://fsf.org/'

     Everyone is permitted to copy and distribute verbatim copies of this
     license document, but changing it is not allowed.

Preamble
========

The GNU General Public License is a free, copyleft license for software
and other kinds of works.

   The licenses for most software and other practical works are designed
to take away your freedom to share and change the works.  By contrast,
the GNU General Public License is intended to guarantee your freedom to
share and change all versions of a program--to make sure it remains
free software for all its users.  We, the Free Software Foundation, use
the GNU General Public License for most of our software; it applies
also to any other work released this way by its authors.  You can apply
it to your programs, too.

   When we speak of free software, we are referring to freedom, not
price.  Our General Public Licenses are designed to make sure that you
have the freedom to distribute copies of free software (and charge for
them if you wish), that you receive source code or can get it if you
want it, that you can change the software or use pieces of it in new
free programs, and that you know you can do these things.

   To protect your rights, we need to prevent others from denying you
these rights or asking you to surrender the rights.  Therefore, you
have certain responsibilities if you distribute copies of the software,
or if you modify it: responsibilities to respect the freedom of others.

   For example, if you distribute copies of such a program, whether
gratis or for a fee, you must pass on to the recipients the same
freedoms that you received.  You must make sure that they, too, receive
or can get the source code.  And you must show them these terms so they
know their rights.

   Developers that use the GNU GPL protect your rights with two steps:
(1) assert copyright on the software, and (2) offer you this License
giving you legal permission to copy, distribute and/or modify it.

   For the developers' and authors' protection, the GPL clearly explains
that there is no warranty for this free software.  For both users' and
authors' sake, the GPL requires that modified versions be marked as
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   Some devices are designed to deny users access to install or run
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   Finally, every program is threatened constantly by software patents.
States should not allow patents to restrict development and use of
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   The precise terms and conditions for copying, distribution and
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TERMS AND CONDITIONS
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     propagate that work, subject to this License.  You are not
     responsible for enforcing compliance by third parties with this
     License.

     An "entity transaction" is a transaction transferring control of an
     organization, or substantially all assets of one, or subdividing an
     organization, or merging organizations.  If propagation of a
     covered work results from an entity transaction, each party to that
     transaction who receives a copy of the work also receives whatever
     licenses to the work the party's predecessor in interest had or
     could give under the previous paragraph, plus a right to
     possession of the Corresponding Source of the work from the
     predecessor in interest, if the predecessor has it or can get it
     with reasonable efforts.

     You may not impose any further restrictions on the exercise of the
     rights granted or affirmed under this License.  For example, you
     may not impose a license fee, royalty, or other charge for
     exercise of rights granted under this License, and you may not
     initiate litigation (including a cross-claim or counterclaim in a
     lawsuit) alleging that any patent claim is infringed by making,
     using, selling, offering for sale, or importing the Program or any
     portion of it.

 11. Patents.

     A "contributor" is a copyright holder who authorizes use under this
     License of the Program or a work on which the Program is based.
     The work thus licensed is called the contributor's "contributor
     version".

     A contributor's "essential patent claims" are all patent claims
     owned or controlled by the contributor, whether already acquired or
     hereafter acquired, that would be infringed by some manner,
     permitted by this License, of making, using, or selling its
     contributor version, but do not include claims that would be
     infringed only as a consequence of further modification of the
     contributor version.  For purposes of this definition, "control"
     includes the right to grant patent sublicenses in a manner
     consistent with the requirements of this License.

     Each contributor grants you a non-exclusive, worldwide,
     royalty-free patent license under the contributor's essential
     patent claims, to make, use, sell, offer for sale, import and
     otherwise run, modify and propagate the contents of its
     contributor version.

     In the following three paragraphs, a "patent license" is any
     express agreement or commitment, however denominated, not to
     enforce a patent (such as an express permission to practice a
     patent or covenant not to sue for patent infringement).  To
     "grant" such a patent license to a party means to make such an
     agreement or commitment not to enforce a patent against the party.

     If you convey a covered work, knowingly relying on a patent
     license, and the Corresponding Source of the work is not available
     for anyone to copy, free of charge and under the terms of this
     License, through a publicly available network server or other
     readily accessible means, then you must either (1) cause the
     Corresponding Source to be so available, or (2) arrange to deprive
     yourself of the benefit of the patent license for this particular
     work, or (3) arrange, in a manner consistent with the requirements
     of this License, to extend the patent license to downstream
     recipients.  "Knowingly relying" means you have actual knowledge
     that, but for the patent license, your conveying the covered work
     in a country, or your recipient's use of the covered work in a
     country, would infringe one or more identifiable patents in that
     country that you have reason to believe are valid.

     If, pursuant to or in connection with a single transaction or
     arrangement, you convey, or propagate by procuring conveyance of, a
     covered work, and grant a patent license to some of the parties
     receiving the covered work authorizing them to use, propagate,
     modify or convey a specific copy of the covered work, then the
     patent license you grant is automatically extended to all
     recipients of the covered work and works based on it.

     A patent license is "discriminatory" if it does not include within
     the scope of its coverage, prohibits the exercise of, or is
     conditioned on the non-exercise of one or more of the rights that
     are specifically granted under this License.  You may not convey a
     covered work if you are a party to an arrangement with a third
     party that is in the business of distributing software, under
     which you make payment to the third party based on the extent of
     your activity of conveying the work, and under which the third
     party grants, to any of the parties who would receive the covered
     work from you, a discriminatory patent license (a) in connection
     with copies of the covered work conveyed by you (or copies made
     from those copies), or (b) primarily for and in connection with
     specific products or compilations that contain the covered work,
     unless you entered into that arrangement, or that patent license
     was granted, prior to 28 March 2007.

     Nothing in this License shall be construed as excluding or limiting
     any implied license or other defenses to infringement that may
     otherwise be available to you under applicable patent law.

 12. No Surrender of Others' Freedom.

     If conditions are imposed on you (whether by court order,
     agreement or otherwise) that contradict the conditions of this
     License, they do not excuse you from the conditions of this
     License.  If you cannot convey a covered work so as to satisfy
     simultaneously your obligations under this License and any other
     pertinent obligations, then as a consequence you may not convey it
     at all.  For example, if you agree to terms that obligate you to
     collect a royalty for further conveying from those to whom you
     convey the Program, the only way you could satisfy both those
     terms and this License would be to refrain entirely from conveying
     the Program.

 13. Use with the GNU Affero General Public License.

     Notwithstanding any other provision of this License, you have
     permission to link or combine any covered work with a work licensed
     under version 3 of the GNU Affero General Public License into a
     single combined work, and to convey the resulting work.  The terms
     of this License will continue to apply to the part which is the
     covered work, but the special requirements of the GNU Affero
     General Public License, section 13, concerning interaction through
     a network will apply to the combination as such.

 14. Revised Versions of this License.

     The Free Software Foundation may publish revised and/or new
     versions of the GNU General Public License from time to time.
     Such new versions will be similar in spirit to the present
     version, but may differ in detail to address new problems or
     concerns.

     Each version is given a distinguishing version number.  If the
     Program specifies that a certain numbered version of the GNU
     General Public License "or any later version" applies to it, you
     have the option of following the terms and conditions either of
     that numbered version or of any later version published by the
     Free Software Foundation.  If the Program does not specify a
     version number of the GNU General Public License, you may choose
     any version ever published by the Free Software Foundation.

     If the Program specifies that a proxy can decide which future
     versions of the GNU General Public License can be used, that
     proxy's public statement of acceptance of a version permanently
     authorizes you to choose that version for the Program.

     Later license versions may give you additional or different
     permissions.  However, no additional obligations are imposed on any
     author or copyright holder as a result of your choosing to follow a
     later version.

 15. Disclaimer of Warranty.

     THERE IS NO WARRANTY FOR THE PROGRAM, TO THE EXTENT PERMITTED BY
     APPLICABLE LAW.  EXCEPT WHEN OTHERWISE STATED IN WRITING THE
     COPYRIGHT HOLDERS AND/OR OTHER PARTIES PROVIDE THE PROGRAM "AS IS"
     WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED OR IMPLIED,
     INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
     MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.  THE ENTIRE
     RISK AS TO THE QUALITY AND PERFORMANCE OF THE PROGRAM IS WITH YOU.
     SHOULD THE PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL
     NECESSARY SERVICING, REPAIR OR CORRECTION.

 16. Limitation of Liability.

     IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN
     WRITING WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MODIFIES
     AND/OR CONVEYS THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU
     FOR DAMAGES, INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL OR
     CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OR INABILITY TO USE
     THE PROGRAM (INCLUDING BUT NOT LIMITED TO LOSS OF DATA OR DATA
     BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD
     PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER
     PROGRAMS), EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF
     THE POSSIBILITY OF SUCH DAMAGES.

 17. Interpretation of Sections 15 and 16.

     If the disclaimer of warranty and limitation of liability provided
     above cannot be given local legal effect according to their terms,
     reviewing courts shall apply local law that most closely
     approximates an absolute waiver of all civil liability in
     connection with the Program, unless a warranty or assumption of
     liability accompanies a copy of the Program in return for a fee.


END OF TERMS AND CONDITIONS
===========================

How to Apply These Terms to Your New Programs
=============================================

If you develop a new program, and you want it to be of the greatest
possible use to the public, the best way to achieve this is to make it
free software which everyone can redistribute and change under these
terms.

   To do so, attach the following notices to the program.  It is safest
to attach them to the start of each source file to most effectively
state the exclusion of warranty; and each file should have at least the
"copyright" line and a pointer to where the full notice is found.

     ONE LINE TO GIVE THE PROGRAM'S NAME AND A BRIEF IDEA OF WHAT IT DOES.
     Copyright (C) YEAR NAME OF AUTHOR

     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
     the Free Software Foundation, either version 3 of the License, or (at
     your option) any later version.

     This program is distributed in the hope that it will be useful, but
     WITHOUT ANY WARRANTY; without even the implied warranty of
     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
     General Public License for more details.

     You should have received a copy of the GNU General Public License
     along with this program.  If not, see `http://www.gnu.org/licenses/'.

   Also add information on how to contact you by electronic and paper
mail.

   If the program does terminal interaction, make it output a short
notice like this when it starts in an interactive mode:

     PROGRAM Copyright (C) YEAR NAME OF AUTHOR
     This program comes with ABSOLUTELY NO WARRANTY; for details type `show w'.
     This is free software, and you are welcome to redistribute it
     under certain conditions; type `show c' for details.

   The hypothetical commands `show w' and `show c' should show the
appropriate parts of the General Public License.  Of course, your
program's commands might be different; for a GUI interface, you would
use an "about box".

   You should also get your employer (if you work as a programmer) or
school, if any, to sign a "copyright disclaimer" for the program, if
necessary.  For more information on this, and how to apply and follow
the GNU GPL, see `http://www.gnu.org/licenses/'.

   The GNU General Public License does not permit incorporating your
program into proprietary programs.  If your program is a subroutine
library, you may consider it more useful to permit linking proprietary
applications with the library.  If this is what you want to do, use the
GNU Lesser General Public License instead of this License.  But first,
please read `http://www.gnu.org/philosophy/why-not-lgpl.html'.

