package visitor.typecase;
import enumeration.Op;

public class Main {
	public static void main (String[] args) {
		Expr one = new Const(1);
		Expr onePtwo = new BinOp (new Const(1), Op.ADD, new Const(2));
		Expr threeMfour = new BinOp (new Const(3), Op.MUL, new Const(4));
		Expr m = new BinOp (onePtwo, Op.SUB, threeMfour);
		Expr n = new BinOp (m, Op.DIV, new Const(5));

		System.out.println (PostorderPrint.run(n));
		System.out.println ("Value: " + Eval.run(n));
	}
}

class PostorderPrint {
	private PostorderPrint() {}
	static private StringBuilder b = new StringBuilder();
	static private StringBuilder runConst(int c) {
		b.append(c + " ");
		return b;
	}
	static private StringBuilder runBinOp(Expr l, Op op, Expr r) {
		run(l); run(r); b.append(op + " ");
		return b;
	}
	static public StringBuilder run(Expr e) {
		if (e instanceof BinOp) {
			BinOp x = (BinOp) e;
			return runBinOp(x.l, x.op, x.r);
		} else {
			Const x = (Const) e;
			return runConst(x.c);
		}
	}
}

class Eval {
	private Eval() {}
	static private Integer runConst(int c) {
		return c;
	}
	static private Integer runBinOp(Expr l, Op op, Expr r) {
		return op.eval(run(l), run(r));
	}
	static public Integer run(Expr e) {
		if (e instanceof BinOp) {
			BinOp x = (BinOp) e;
			return runBinOp(x.l, x.op, x.r);
		} else {
			Const x = (Const) e;
			return runConst(x.c);
		}
	}
}