/**
* 弹出(组装好的)操作符
*
* @return 操作符
*/
Operator popOperator() {
if (operatorStack.isEmpty())
throw I18nExceptionFactory.createIllegalStateException(
"ExpressionReducer.miss.left.parenthesis");
Operator operator = (Operator) operatorStack.pop();
// 从参数栈弹出所需参数组装操作表达式
if (operator instanceof BinaryOperator) {
BinaryOperator binaryOperator = (BinaryOperator) operator;
if (parameterStack.isEmpty())
throw I18nExceptionFactory.createIllegalStateException(
"ExpressionReducer.operator.miss.parameter");
Expression rightParameter = (Expression) parameterStack.pop(); // 调整参数顺序
if (parameterStack.isEmpty())
throw I18nExceptionFactory.createIllegalStateException(
"ExpressionReducer.operator.miss.parameter");
Expression leftParameter = (Expression) parameterStack.pop();
parameterStack.push(
populateBinaryOperator(
(BinaryOperatorImpl) binaryOperator,
leftParameter,
rightParameter)); // 将组装好的表达式作为参数压入
} else if (operator instanceof UnaryOperator) {
UnaryOperator unaryOperator = (UnaryOperator) operator;
if (parameterStack.isEmpty())
throw I18nExceptionFactory.createIllegalStateException(
"ExpressionReducer.operator.miss.parameter");
Expression parameter = (Expression) parameterStack.pop();
parameterStack.push(
populateUnaryOperator((UnaryOperatorImpl) unaryOperator, parameter)); // 将组装好的表达式作为参数压入
}
return operator;
}
/**
* 弹出(最后的)结果
*
* @return 结果
*/
Expression popResult() {
while (!operatorStack.isEmpty()) {
Operator operator = popOperator(); // 弹出栈中所有操作符
if (operator == Parenthesis.LEFT_PARENTHESIS)
throw I18nExceptionFactory.createIllegalStateException(
"ExpressionReducer.miss.right.parenthesis");
}
Expression result = (Expression) parameterStack.pop();
Assert.assertTrue(
parameterStack.isEmpty(), "ExpressionReducer.operator.miss.parameter"); // 后验条件
return result;
}