[cl-unification-devel] newbie; questions on comutivity.

As someone exposed to unification through languages like prolog and kanren, I'm a little puzzled as to why the following doesn't seem to commute: CL-USER> (let ((e (unify '(42 ?a) '(?a ?b)))) (values (v? '?b e) (v? '?a e))) 42 42 CL-USER> (let ((e (unify '(?a ?b) '(42 ?a)))) (values (v? '?b e) (v? '?a e))) ?A 42 CL-USER> If this is correct behavior, could someone explain it to me? Thank you, Matt -- "You do not really understand something unless you can explain it to your grandmother." -- Albert Einstein.