function calculate(){
	var left = Number(leftOperandText.getValue());
	var right = Number(rightOperandText.getValue());
	var result = NaN;
	
	switch (operatorCombo.getValue()) {
	case "+":
		result = left + right;
		break;
	case "-":
		result = left - right;
		break;
	case "*":
		result = left * right;
		break;
	case "/":
		result = left / right;
		break;
	}

	resultText.setValue(result);
}
