How to enable the occurs check in all unifications in SWI-Prolog?
问题 According to Wikipedia: Implementations offering sound unification for all unifications are Qu-Prolog and Strawberry Prolog and (optionally, via a runtime flag): XSB, SWI-Prolog and Tau Prolog. However, when I do apropos(occur) it only finds unify_with_occurs_check/2 . The man page doesn't mention "occur" either. How can the occurs check be enabled for all unifications in SWI-Prolog? 回答1: In the section on Environment Control, it lists the flags of the system. The occurs_check flag is the one