package enumeration;

public abstract class Op {
	private final String name;
	Op(String name) { this.name = name; }
	public String toString() { return name; }

	public abstract int eval(int x, int y);

	public static final Op ADD = new OpAdd();
	public static final Op SUB = new OpSub();
	public static final Op MUL = new OpMul();
	public static final Op DIV = new OpDiv();
}

final class OpAdd extends Op {
	OpAdd() {  super("+"); }
	public int eval(int x, int y) { return x+y; }
}
final class OpSub extends Op {
	OpSub() {  super("-"); }
	public int eval(int x, int y) { return x-y; }
}
final class OpMul extends Op {
	OpMul() {  super("*"); }
	public int eval(int x, int y) { return x*y; }
}
final class OpDiv extends Op {
	OpDiv() {  super("/"); }
	public int eval(int x, int y) { return x/y; }
}