gnu-prolog

I'm reading "Seven languages in seven weeks" atm, and I'm stumped over some Prolog query that I don't understand the 'no' response to. The friends.pl file looks like this: likes(wallace, cheese). likes(grommit, cheese). likes(wendolene, sheep). friend(X, Y) :- \+(X = Y), likes(X, Z), likes(Y, Z). I can do some trivial queries on it, such as: | ?- ['friends']. compiling /home/marc/btlang-code/code/prolog/friends.pl for byte code... /home/marc/btlang-code/code/prolog/friends.pl compiled, 12 lines read - 994 bytes written, 8 ms yes | ?- friend(wallace,grommit). yes | ?- friend(wallace,wendolene).

another way to ask the question is: How I can list all the properties of an atom? For example: movie(agora). director(agora, 'Alejandro Amenabar') duration(agora, '2h'). so, I will like to receive all the predicates that has agora for argument. In this case it will be: movie, director, duration, with the other parameters ('Alejandro Amenabar', '2h'). I found: this , and this questions, but I couldn't understand well. I want to have value of false in the "variable Answer" if PersonInvited doesn't like something about the movie. My query will be: answer(Answer, personInvited,

I'd like to use predicates like: range(X,0,5) range(X,4,200) range(X,-1000000,1000000) dom_range(X,-1000000,1000000) with meaning : range(X,0,5) :- member(X,[0,1,2,3,4,5]). range(X,4,200) :- member(X,[4,5,6...198,199,200]). range(X,-1000000,1000000) :- member(X,[-1000000,...,1000000]). dom_range(X,-1000000,1000000) :- domain(X, [-1000000,...,1000000]). How to code it in Prolog nicely (taking solution performance into account - depth of recursion etc) ? Solution is expected to run on GNU-Prolog. P.S. Question inspired with this question . SWI-Prolog has the predicate between/3 . so you would

There is a lack of some predicates in one Prolog implementations, that are available in others. We can implement lacking predicates, let's call this "Prolog Compatibility Layer". Do you know "Prolog Compatibility Layers" for Prolog (especially for GNU-Prolog) ? Please structure answers in following way: Title with link. "Implemented for" - prolog implementation you might like to use "Compatibility with" - prolog implementation for which compatibility layer is done "Functions" - list of compatibility functions (you can bold yours favourites) "Additional info" - comments, requirements,

While using gprolog I often have exceptions without any kind of line numbers or context like this one: uncaught exception: error(instantiation_error,(is)/2) Without any kind of context. I know I can do a trace but it would take very long to debug it with trace since I need to execute a lot of things before getting to the place where the error occur. Any idea on how to have this stacktrace ? Or a dynamic trace / notrace ? EDIT: Or just automate the printing of the whole trace output. @gusbro's answer ( s(X) ) shows you how you somewhat solve this with GNU's debugger. However, if you cannot