4.7 Comparison and Unification of Terms
AllApplicationManualNameSummaryHelp

Availability:built-in
[ISO]?Term1 = ?Term2
Unify Term1 with Term2. True if the unification succeeds. For behaviour on cyclic terms see the Prolog flag occurs_check. It acts as if defined by the following fact: 
=(Term, Term).
ClioPatria (version V3.1.1-21-gb8003bb)