SWI-Prolog -- ord_memberchk/2

Availability::- use_module(library(ordsets)).(can be autoloaded)

[semidet]ord_memberchk(+Element, +OrdSet)

True if Element is a member of OrdSet, compared using ==. Note that enumerating elements of an ordered set can be done using member/2.

Some Prolog implementations also provide ord_member/2, with the same semantics as ord_memberchk/2. We believe that having a semidet ord_member/2 is unacceptably inconsistent with the *_chk convention. Portable code should use ord_memberchk/2 or member/2.

author: Richard O'Keefe