iso_dif/2 is much simpler to implement than a comparison: The built-in \= operator is available You now exactly what arguments to provide to\= Definition Based on your comments, the safe comparison means that the order won’t change if variables in both subterms are instanciated. If we name the comparison lt, we have for example: lt(a(X), … Read more
Correct, this is a warning to enforce best practices, which is to put all related clauses together in the source file. Other than that, the proximity of clauses to each other in the source file does not matter, as long as their relative order does not change.
Third attempt. This is mainly a bugfix in a previous answer (which already had many modifications). Edit: 06/04/2015 When creating a more general term I was leaving both subterms as-is if either of them was a variable. Now I build a more general term for the “other” subterm in this case, by calling term_general/2. unify_sto(X,Y):- … Read more
Single quoted items are always atoms. The meaning of double quotes depends on the Prolog flag double_quotes: atom — with this value “a” = a. Nowadays, this is rarely used. But you will find Prolog books where [“abc.pl”] is written. codes — a list of character codes. This is frequently the default, but it leads … Read more
avs_term_rearranged(AVs, T, AVsR) :- term_variables(T, Vs), copy_term(Vs+AVs, Vs1+AVs1), bind_names(AVs1), build_vn_list(Vs, Vs1, AVsR). bind_names([]). bind_names([N=V|AVs]) :- N = V, bind_names(AVs). build_vn_list([], [], []). build_vn_list([V|Vs],[N|Ns],NVs) :- ( atom(N) -> NVs = [N=V|NVs1] ; var(N) -> NVs = NVs1 ), build_vn_list(Vs, Ns, NVs1).
Yes, there is such a control construct in ISO Prolog, called ->. You use it like this: ( condition -> then_clause ; else_clause ) Here is an example that uses a chain of else-if-clauses: ( X < 0 -> writeln(‘X is negative. That’s weird! Failing now.’), fail ; X =:= 0 -> writeln(‘X is zero.’) … Read more