Some pure predicates that I learned from others.

 =(?X, ?Y, ?Truth)

 if_(:If_1, :Then_0, :Else_0)

 list_item_isMember(?L, ?X, ?Truth)

 list_list_intersection(?Xs, ?Ys, ?Zs)

Re-exported predicates

The following predicates are exported from this file while their implementation is defined in imported modules or non-module files loaded by this module.

 dif(+Term1, +Term2) is semidet

Constraint that expresses that Term1 and Term2 never become identical (==/2). Fails if Term1 == Term2. Succeeds if Term1 can never become identical to Term2. In other cases the predicate succeeds after attaching constraints to the relevant parts of Term1 and Term2 that prevent the two terms to become identical.