Sather Home Page

Section 8.1.1.14:
$ORDERED

abstract class $ORDERED{TYP} < $VALUE, $IS_LT{TYP}

$IS_NIL $NIL $IS_EQ $VALUE $IS_LT{TYP} $ORDERED{TYP}
Inheritance Diagram

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 ;
$ORDERED = set of object_type

state

references : $ORDERED
   inv ref_types ==
      forall obj | obj in set ref_types &
         sub_type($ORDERED,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 a value for which ordering is possible in addition to equality and nil testing and a nil value.

This class defines no features of itself, deriving those features which sub-types must implement transitively from the abstractions from which it inherits.


Language Index Library Index Basic Index
Comments or enquiries should be made toKeith Hopper.
Page last modified: Thursday, 31 May 2001.
Produced with Amaya