Question 1: Prolog systems are not always able to decide whether or not a clause will apply prior to executing it. The precise circumstances are implementation dependent. That is, you cannot rely on that decision in general. Systems do improve here from release to release. Consider as the simplest case: ?- X = 1 ; … Read more
Have a look at: http://www.swi-prolog.org/FAQ/AllOutput.html The simple solution is to type w after the answer is given, i.e.: ?- n_queens_problem(10,X). X = [1, 3, 6, 8, 10, 5, 9, 2, 4|…] [write] X = [1, 3, 6, 8, 10, 5, 9, 2, 4, 7] After you have pressed the “w”-key “[write]” is displayed at the … Read more
It’s useful, but in my opinion not yet ideal because I cannot cut duplicate paths at the point of their creation. Consider, with the complete graph K_n: n_complete(N, Es) :- numlist(1, N, Ns), phrase(pairs(Ns), Es). adjacent(Edges, X, Y) :- member(edge(X, Y), Edges). pairs([]) –> []. pairs([N|Ns]) –> edges(Ns, N), pairs(Ns). edges([], _) –> []. edges([N|Ns], … Read more