public class Func {

	enum OP_TYPE{
		VALUE,
		ADDITION,
		SUBTRACTION,
		MULTIPLICATION,
		DIVISION
	}
	
	
	OP_TYPE op;
	Func left;
	Func right;
	float value;

	public Func(OP_TYPE op, Func left, Func right){
		this.op = op;
		this.left = left;
		this.right = right;
	}
	
	public Func(float value){
		this.op = OP_TYPE.VALUE;
		this.value = value;
	}
	
	public static Func createFunc(String formula){
		Func func = null;
		
		for(int i = formula.length() - 1; i > 0; i--){
			if(formula.charAt(i) == '+'){
				System.out.println("Create addition: " + formula);
				String a = formula.substring(0, i); //5
				String b = formula.substring(i + 1, formula.length());  //4
				func = new Func(Func.OP_TYPE.ADDITION, a, b);
				return func;
			} else if(formula.charAt(i) == '-'){
				System.out.println("Create subtraction: " + formula);
				String a = formula.substring(0, i); //5
				String b = formula.substring(i + 1, formula.length());  //4
				func = new Func(OP_TYPE.SUBTRACTION, a, b);
				return func;
			}
		}
		System.out.println("Create value: " + formula);
		float value = Float.parseFloat(formula);
		func = new Func(value);

		return func;
	}
	public void printONP(){
		if(op == OP_TYPE.VALUE){
			System.out.print(value);
		}else {
			System.out.print(opToText());
			left.printONP();
			right.printONP();
		}
	}
	
	String opToText(){
		switch(op){
			case ADDITION:
				return "+";
			case SUBTRACTION:
				return "-";
		}
		return "?";
	}
	
	public Func(OP_TYPE op, String left, String right){
		this.op = op;
		this.left = createFunc(left);
		this.right = createFunc(right);
	}
	
	public float calc(){
		if(op == OP_TYPE.ADDITION){
			return left.calc() + right.calc();
		}else if(op == OP_TYPE.SUBTRACTION){
			return left.calc() - right.calc();
		}else if(op == OP_TYPE.VALUE){
			return value;
		}
		return 0.0f;
	}
}