Problem in clause/2

[gciatto]

There is a problem in the clause/2 behavior. If I ask for the body of a clause, it will not use the same variable set of the head, making it impossible to unify them.

For example, given the clause:

head(X) :- body(X).

the query clause(head(X), Body) returns Body = body(X1), where X and X1 are different.