
variant(?Term1, ?Term2)

   Succeeds if Term1 is a variant of Term2.



Arguments
   Term1               An arbitrary term.
   Term2               An arbitrary term.

Type
   Comparing and Sorting

Description
   Succeeds if the given terms are equal in the sense that all
   ground instantiations in Term1 are also instantiations in Term2 and vice
   versa.  The result is undefined if Term1 and Term2 share variables.  No
   unification is performed.

   Attributed variables are handled via the attribute's compare_instances
   handler.  In particular, domain variables should be handled correctly.



Modes and Determinism
   variant(?, ?) is semidet

Fail Conditions
   Fails if Term1 is not a variant of Term2.

Examples
   
   Success:
   variant(1,1).
   variant(X,Y).
   variant(f(a,b),f(a,b)).
   variant(f(a,X),f(a,Y)).
   variant(f(X,Y),f(Y,X)).
   variant([X,2], [Y,2]).
   [X,Y]::2..4, variant(X,Y).

   Fail:
   variant(f(a,b),f(a,Y)).
   variant(f(a,X),f(a,b)).
   variant(f(X,Y),f(Z,Z)).
   X::2..4, Y::1..5, variant(X,Y).


See Also
   instance / 2, compare_instances / 3, prune_instances / 2
