lab05

/*
Design Pattern Composite:

Client => Test
Component => Expression
Composite => Operador


*/

abstract class Expression {
	//Expression left, right;

	abstract float eval();
	abstract void add(Expression exp);
	//void remove (Expression exp);
	//Expression getChild (int index);
}

class Operand extends Expression {
    float value;

    Operand (float value) {
       this.value = value;
    }

	float eval() {
		return this.value;
	}

	void add(Expression exp){}
	void remove(Expression exp){}
	Expression getChild (int index){
		return null;
	}
}

abstract class Operator extends Expression {
	Expression left, right;

    void add (Expression exp){
    	if (right == null) right = exp;
    	else left = exp;
    }

    float eval(){
    	return 0;
    }

	void remove (Expression exp){}
	Expression getChild (int index){
		return null;
	}

}

class Multi extends Operator {
	float eval (){
 		 return left.eval() * right.eval();
	}
}

class Div extends Operator {
	float eval (){
 		 return left.eval() / right.eval();
	}
}


public class Test {
	public static void main (String args[]) {
		Expression root, m;
		m = new Multi ();
		m.add(new Operand(2));
		m.add(new Operand(3));

		root = new Div ();
		root.add(new Operand(4));
		root.add(m);

		System.out.println(root.eval());
	}
}