> > GNU Prolog 1.3.1 > > By Daniel Diaz > > Copyright (C) 1999-2009 Daniel Diaz > > | ?- even(X). > > uncaught exception: error(existence_error(procedure,even/1),top_level/0) > > I'm a bit rusty, and only just installed gprolog myself, and am not > familiar with its messages. But it looks to me like there is no > predicate 'even/1' defined -- "existence_error(procedure,even/1).
"existence_error" means there is no such predicate available to the interpreter: it is neither a built-in nor user construct. Amongst other places, the Gprolog docs are at http://www.gprolog.org/manual/html_node/index.html and you can find the builtin predicates in http://www.gprolog.org/manual/html_node/gprolog-idx.html To create a user defined predicate, even/1, you would open a text file, called test2.pl with notepad (or some other text editor) and enter the line: even(X):- U is X mod 2, !,U == 0. save the file and at the interpreter prompt enter | ?- [test2]. and then | ?- even(12). So now U have defined a user predicate called even that tests for "evenness" with the mod function. Dhu > > Try something like reverse([1,2,3],X). If that doesn't work, you have > an installation error. > > > > > not sure if the installation was wrong, but got not errors or I'm missing > > something very simple. > > also is there a good FAQ's page for this interpreter. > > Google "gprolog tutorial" I get lots of hits. I think you need a tutorial > rather than a FAQ. Work through some of these. > > > > > many thanks > > > > James. > > > > ps. sorry if this is a silly posting but didn't know what else to try :S > > Good luck. This looks like a low traffic list, so I thought I'd go ahead > and answer > instead of waiting for a expert. > > John Velman > > > > > ------------------------------ > > _______________________________________________ > Users-prolog mailing list > Users-prolog@gnu.org > http://lists.gnu.org/mailman/listinfo/users-prolog > > > End of Users-prolog Digest, Vol 71, Issue 5 > ******************************************* > _______________________________________________ Users-prolog mailing list Users-prolog@gnu.org http://lists.gnu.org/mailman/listinfo/users-prolog
