// h18.9/29 (鈴)
package exp;

import tiny_prolog.Core;

/** Core の実験 */
public class P0 extends Core
{
    static Goal _(Pred pred, Object... terms) {
        return new Goal (pred, terms);
    }
    
    static Goals __(Goal goal) {
        return new Goals (goal, null);
    }
    
    static Pair<Object, Object> cons(Object car, Object cdr) {
        return new Pair<Object, Object> (car, cdr);
    }

    /** append 述語を定義し，実行結果を表示する。 */
    public static void main(String[] args) {
        Var A = new Var ("A");
        Var X = new Var ("X");
        Var Y = new Var ("Y");
        Var Z = new Var ("Z");
        Pred append = new Pred ("append");

        // append([], A, A).
        _(append, null, A, A).si(null);

        // append([A|X], Y, [A|Z]) :- append(X, Y, Z).
        _(append, cons(A, X), Y, cons(A, Z)).si(__(_(append, X, Y, Z)));

        // ?- append(X, Y, [1, 2, 3]).
        Goals goals = __(_(append, X, Y, cons(1, cons(2, cons(3, null)))));

        for (Env env: goals) {
            Object x = env.get(X);
            Object y = env.get(Y);
            System.out.println("x = " + x + ", y = " + y);
        }
    }
}