Programming Languages

3.3. Logic Programming

Logic programming uses formal logic, expressing programs as facts and rules. The system infers solutions via unification and backtracking.

Core Principles

Facts and Rules: Define relationships.

Queries: Ask the system to deduce answers.

Backtracking: Tries alternative solutions.

Declarative: Logic-focused, not procedural.

Example (Java with tuProlog)

Java integrates logic programming via libraries like tuProlog

import alice.tuprolog.*;

public class LogicExample {

    public static void main(String[] args) throws Exception {

        Prolog engine = new Prolog();

        engine.addTheory(new Theory(

            "parent('John', 'Mary').\n" +

            "parent('Mary', 'Alice').\n" +

            "grandparent(X, Z) :- parent(X, Y), parent(Y, Z)."

        ));

        SolveInfo info = engine.solve("grandparent('John', 'Alice').");

        System.out.println(info.isSuccess()); // Output: true

    }

}