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variant(?Term1, ?Term2)
Succeeds if Term1 is a variant of Term2.
- Term1
- An arbitrary term.
- Term2
- An arbitrary term.
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
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