python (65.2k questions)

javascript (44.3k questions)

reactjs (22.7k questions)

java (20.8k questions)

c# (17.4k questions)

html (16.3k questions)

r (13.7k questions)

android (13k questions)

Questions - prolog

Prolog: Why is member/2 not working properly here?

I encountered an interesting problem: In my code, [R|Rs] is the rest of a list generated by removing Seq from SortedRanks. It is going to have 1 or 2 elements. The number depends on the length of Seq,...
test-img

Emanuele Filiberto

prolog

Votes: 0

Answers: 1

Latest Answer

I can't tell what you're doing without any examples, but I suspect "even though Rs is in it" is not accurate; I guess your problem is that in [R|Rs], Rs is a list not an element. If the len...
test-img

TessellatingHeckler

How to bi-unify a term's operator in Prolog?

I just asked the question in How to unify a term's operator in Prolog? and got good answers. However, it doesn't completely solve my problem, i.e. =.. only works for single-side. For example, test...
test-img

chansey

prolog

Votes: 0

Answers: 1

Latest Answer

expr_op_x_y(Expr, Op, X, Y) :- when((nonvar(Expr) ; nonvar(Op)), Expr =.. [Op, X, Y]). ?- expr_op_x_y(Expr, Op, X, Y). when((nonvar(Expr);nonvar(Op)),Expr=..[Op,X,Y]). ?- expr_op_x_y(Expr, Op, ...
test-img

false

How to unify a term's operator in Prolog?

I can unify operands in SWI-Prolog, for example: ?- +(X,Y) = 1 + 2. X = 1, Y = 2. but how to unify an operator? ?- Op(X,Y) = 1 + 2. ERROR: Syntax error: Operator expected I hope Prolog to return X =...
test-img

chansey

prolog

Votes: 0

Answers: 1

Latest Answer

You unify terms. Both +(1,2) and 1 + 2 are the same term. You may use the univ predicate (=..) to decompose a term like this: ?- 1+2 =.. [Op, X, Y]. Op = (+), X = 1, Y = 2.
test-img

gusbro

Prolog: Can't increase value of variable inside complex term

So I'm working on a prolog problem where a state is defined in a complex term, When I try to increase the value of x inside this complex term nothing happens for example CurrentState(left, x, y). t...
test-img

user15916724

syntax

prolog

Votes: 0

Answers: 1

Latest Answer

Facts and predicates need to start with a lowercase letter. Variables need to start with an uppercase letter. = is not assignment, and Prolog predicates aren't function calls, and you never use test a...
test-img

TessellatingHeckler

Posts

Questions

Blogs

Jobs