# Section 8.10.1.6:
$OPTION

###### abstract class $OPTION < $INSTR

#### Formal Definitions

This abstract class defines a state component which is a set of all instantiations of objects of any class sub-typing from this class in addition to the vdm model types used wherever this class name is used. Note that SAME has to be an instantiated class, not an abstract one.

types
SAME = object_type ;
$OPTION = set of object_type
state
multi : $OPTION
inv multi_types ==
forall obj in set multi_types & sub_type($OPTION,obj)

NOTE | See the important note about vdm state in the notes on vdm-sl usage in this specification.

This abstraction encapsulates the notion of a program option argument. An option may be of any kind for which an external textual representation is provided and suitable for reading.

This class defines no features.

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Comments or enquiries should be made to Keith Hopper. Page last modified: Friday, 17 November 2000. |