% Define parent-child relationships
parent(alice, bob).
% Define a rule to perform unification
unify_predicate(Y) :-
parent(alice, bob), % First predicate
parent(alice, Y). % Second predicate with a variable
% Main function to perform the query and print the result
main :-
unify_predicate(Y),
write('Unify Y = '), write(Y), nl.
% Test case for unification
test_unification :-
main.
% Test case for failure when parent/3 is used
test_failure :-
\+ (parent(alice, _, _) ; parent(_, _, alice)),
write('Unification failed'), nl.
% Initialization directive for the unification test case
:- initialization(test_unification).
% Initialization directive for the failure test case
:- initialization(test_failure).
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Prolog (Programming in Logic) is a logic programming language associated with artificial intelligence and computational linguistics. It works through facts, rules, and queries, using a form of symbolic reasoning known as backward chaining. Prolog is declarative, meaning you describe what you want instead of how to compute it.
The following is a simple Prolog program that prints a greeting:
:- initialization(main).
main :-
write('Hello, World!').
Facts represent basic assertions about the world.
likes(alice, pizza).
likes(bob, pasta).
Rules define logical relationships using facts.
friends(X, Y) :- likes(X, Z), likes(Y, Z).
Queries are used to find information based on facts and rules.
?- likes(alice, What).
| Operator | Description |
|---|---|
:- | Rule definition |
, | Logical AND |
; | Logical OR |
= | Unification |
member(X, [X|_]).
member(X, [_|T]) :- member(X, T).
Prolog heavily relies on recursion.
factorial(0, 1).
factorial(N, F) :-
N > 0,
N1 is N - 1,
factorial(N1, F1),
F is N * F1.
This guide provides a quick reference to Prolog programming syntax and features. Start writing Prolog code using OneCompiler’s Prolog online compiler today!