Hi Dear sirs let's look at code :- module tst2. :- interface. :- import_module io. :- pred main(io, io). :- mode main(di, uo) is det. :- implementation. :- import_module solutions, list, int. main --> { promise_equivalent_solutions [L] unsorted_solutions((pred(E::out) is nondet :- member(E, 1..20), E mod 3 = 0 ), L) }, print(L). Note, that without "promise_equivalent_solutions [L]" it gives $ mmc tst2 tst2.m:008: In `main'(di, uo): tst2.m:008: error: determinism declaration not satisfied. tst2.m:008: Declared `det', inferred `multi'. tst2.m:017: call to `solutions.unsorted_solutions'((pred(out) is nondet), tst2.m:017: out) can succeed more than once. tst2.m:017: Error: call to predicate `solutions.unsorted_solutions'/2 with tst2.m:017: determinism `cc_multi' occurs in a context which requires all tst2.m:017: solutions. while compiling. I've read some documentation on cc_multi, and I seem to understand the meaning of cc_multi. It's used when we defining predicate as being multi, but using it in place where we nead only 1 solution (actually, anyone.. this is determined by compiler what solution to return taking in mind optimization concerns). What I can't understand is why should I explicitely convert it to det with "promise_equivalent_solutions [L]". Why compiler is not smart enough to make this automatically? I know that I could alternatively make cc_multi my main predicate.. But what if I have some architecture with many det predicates. This would mean that I should then turn all those preds to cc_multi.. I don't like this.. I've also read this thread that seem to relate to my questions <a href="http://www.mercury.csse.unimelb.edu.au/mailing-lists/mercury-developers/mercury-developers.0108/0034.html">http://www.mercury.csse.unimelb.edu.au/mailing-lists/mercury-developers/mercury-developers.0108/0034.html</a> but still it's not very clear. Also, it seems not very logical to me that aggregate and solutions predicates perform sorting & removing duplicates. It seems more logical that those perform as their unsorted_ counterparts and additional sorted_ versions be present. I beg pardon for my, most likely, stupid questions =) Sincerely yours, Vladimir