Prolog pattern matching is based on unification, specifically the Martelli-Montanari Algorithm (minus the occurs check, by default). This algorithm matches values of the same position, binding variables on one side to a value at corresponding position on the other side. This kind of pattern matching could work both ways, therefore in Prolog you could use … Read more
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
The most elaborate Prolog IDE I’m familiar with is the Eclipse-based IDE for Amzi! Prolog. This is a commercial product, but the IDE can be downloaded and used for free in the Student Edition. It might be ideal for a beginning Prolog programmer. Disclaimer: I may be biased because I supply a lot of free … Read more
The = “operator” in Prolog is actually a predicate (with infix notation) =/2 that succeeds when the two terms are unified. Thus X = 2 or 2 = X amount to the same thing, a goal to unify X with 2. The == “operator” differs in that it succeeds only if the two terms are … Read more
Well for one thing, the name should be more declarative, like equality_truth/2.
You may want to use pyDatalog, a logic programming library that I developed for Python implementing Datalog. It also works with SQLAlchemy to query relational databases using logic clauses.
This is usually called maplist/3 and is part of the Prolog prologue. Note the different argument order! :- meta_predicate(maplist(2, ?, ?)). maplist(_C_2, [], []). maplist( C_2, [X|Xs], [Y|Ys]) :- call(C_2, X, Y), maplist( C_2, Xs, Ys). The different argument order permits you to easily nest several maplist-goals. ?- maplist(maplist(test),[[1,2],[3,4]],Rss). Rss = [[1,4],[9,16]]. maplist comes in … Read more
I think the above answer deserves a few words of explanation here nevertheless. A short note in advance: Arithmetic expressions in Prolog are just terms (“Everything is a term in Prolog”), which are not evaluated automatically. (If you have a Lisp background, think of quoted lists). So 3 + 4 is just the same as … Read more
If you want to study termination properties in depth, programs using successor-arithmetics are an ideal study object: You know a priori what they should describe, so you can concentrate on the more technical details. You will need to understand several notions. Universal termination The easiest way to explain it, is to consider Goal, false. This … Read more
I would like to focus on one important general point I noticed when working with different interfaces for attributes variables: When designing an interface for attributed variables, an implementor should also keep in mind the following: Is it possible to take attributes into account when reasoning about simultaneous unifications, as in [X,Y] = [0,1]? This … Read more