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Section 8.2.1.1:
$BIT_PATTERNS

abstract class $BIT_PATTERNS < $IS_EQ

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 ;
$BIT_PATTERNS = set of object_type

state
multi : $BIT_PATTERNS
   inv multi_types ==
      forall obj | obj in set multi_types &
         sub_type($BIT_PATTERNS,obj)
NOTE See the important note about vdm state in the notes on vdm-sl usage in this specification.

This abstract class models the concept of an object for which the values are arbitrary bit-patterns to which no semantics is attached save the count of the number of bits - the only feature specified.


asize

Since the implementations of classes sub-typing from this abstraction necessarily use the pervasive AVAL constructor class, this reader routine must be defined - to indicate the number of contiguous bits of which an object of the class consists.

asize : CARD

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