Reification of term equality/inequality

Question

Pure Prolog programs that distinguish between the equality and inequality of terms in a clean manner suffer from execution inefficiencies ; even when all terms of relevance

Answer 1

It seems to be best to call this predicate with the same arguments (=)/3. In this manner, conditions like if_/3 are now much more readable. And to use rather the suffix _t in place of _truth:

memberd_t(_X, [], false).
memberd_t(X, [Y|Ys], Truth) :-
   if_( X = Y, Truth=true, memberd_t(X, Ys, Truth) ).

Which used to be:

memberd_truth(_X, [], false).
memberd_truth(X, [Y|Ys], Truth) :-
   if_( equal_truth(X, Y), Truth=true, memberd_truth(X, Ys, Truth) ).