I normally was able to figure out some usages of Lambda with maplist, but in general have hard time using lambda in prolog. It is probably because it differ from other languages, because of unifica...

Are Hilog terms (i.e. compounds having as functors arbitrary terms) still regarded as a powerful feature in XSB Prolog (or any other Prolog) ? Are there many XSB projects currently using this featu...

?- assertz(:- module(foo1, [f/1])). true. ?- foo1:assertz(f(1)). true. ?- foo1:f(1). true. ?- foo2:f(1). Correct to: "foo1:f(1)"? no ERROR: Undefined procedure: foo2:f/1 ERROR: In: ERROR: [8] fo...

I am trying to define a relation callto_status(Goal, Status) that always succeeds and unifies Status according to the result of calling Goal (in other words, I would like to implement a reified ver...

I'm currently working on a very short project on Prolog, and just got stuck trying to apply a "filter" I have created to a list. I have what you could call the filter ready, but I can't apply it. I...

Suppose I want to write a custom operator for composing DCG rules in a way that would otherwise be repetitive. For example, suppose I had I a DCG, ws such that: ws --> []. ws --> " ", ws. ...

This is a question provoked by an already deleted answer to this question. The issue could be summarized as follows: Is it possible to fold over a list, with the tail of the list generated while...

Given the following facts in a database: foo(a, 3). foo(b, 2). foo(c, 4). foo(d, 3). foo(e, 2). foo(f, 6). foo(g, 3). foo(h, 2). I want to collect all first arguments that have the smallest seco...

Using SWI-Prolog (Multi-threaded, 64 bits, Version 7.3.5), we proceed step by step: Define dcg nonterminal a//1 in module dcgAux (pronounced: "di-SEE-goh"): :- module(dcgAux,[a//1]). a(0) --> ...

Many predicates define some kind of an acyclic path built from edges defined via a binary relation, quite similarly to defining transitive closure. A generic definition is thus called for. Note tha...

In sicstus prolog, there's a predicate: maplist(:Pred, +List) Pred is supposed to take just one argument - List element. How can I pass a 2-argument predicate, with first argument defined? In ot...

In CLP(FD), we frequently need to state: "This is a list of integers and finite domain variables in (sometimes: strictly) ascending/descending order." Is there any CLP(FD) system that provides a g...

To calculate the hamming distance between two lists of the same length, I use foldl(hamm, A, B, 0, R). with this definition of hamm/4: hamm(A, A, V, V) :- !. hamm(A, B, V0, V1) :- A \= B, V1 is V0...

The following higher order predicate succeeds if all pairs of the list's elements are true for a given relation. Is there a common or better, more intention revealing name for this relation? My or...

Many predicates essentially use some form of transitive closure, only to discover that termination has to be addressed too. Why not solve this once and forever with closure0/3: :- meta_predicate(cl...

This is the code that i am trying to understand. co(X) :- co(X,[],L). co([],A,A):- write(A). co([X|Xs], A, L) :- p(X-Z,A,R), !, Z1 is Z+1, co(Xs, [X-Z1|R], L). co([X|Xs], A, L) :- co(Xs, [X-1|A],...

So the univ operator. I don't exactly understand it. For example this: foo(PredList,[H|_]) :- bar(PredList,H). foo(PredList,[_|T]) :- foo(PredList,T),!. bar([H|_],Item) :- G =.. [H,Item],G. bar(...

How do you write a Prolog procedure map(List, PredName, Result) that applies the predicate PredName(Arg, Res) to the elements of List, and returns the result in the list Result? For example: test...