
compare_instances(-Relationship, ?Term1, ?Term2)

   Succeeds if Relationship is an atom describing the instance relationship
between Term1 and Term2.



Arguments
   Relationship        Variable or one of the atoms '<', '>', '='
   Term1               An arbitrary term.
   Term2               An arbitrary term.

Type
   Comparing and Sorting

Description
   Succeeds if Relationship is unified with one of the three term
   relationship symbols indicated by '<', '>', '=' where:


   '<':  Term1 is an instance of Term2.


   '>':  Term2 is an instance of Term1.


   '=':  Term1 is variant of Term2.


   For the definition of instance and variant refer to instance/2 and
   variant/2, respectively.




Modes and Determinism
   compare_instances(-, ?, ?) is det

Fail Conditions
   Fails if none of the terms is an instance of the other

Examples
   
   Success:
   compare_instances(Rel,X,Y), Rel == '='.
   compare_instances(=, [a,X], [a,Y]).
   compare_instances(<, [a,b], [X,Y]).
   compare_instances(<, [X], [X|Y]).
   compare_instances(>, X, f(1,1)).
   compare_instances(<, f(1,1), X).
   Fail:
   compare_instances(Rel, f(X), 1).
   compare_instances(Rel, 1, f(X)).
   compare_instances(<, X, a).





See Also
   instance / 2, variant / 2
