请用c++利用顺序栈实现表达式的求解

以下是使用顺序栈实现表达式求解的 C++ 代码：

#include <iostream>
#include <stack>
#include <string>

using namespace std;

int priority(char op) {
    if (op == '+' || op == '-') {
        return 1;
    } else if (op == '*' || op == '/') {
        return 2;
    } else if (op == '^') {
        return 3;
    } else {
        return -1;
    }
}

double calculate(double num1, double num2, char op) {
    switch(op) {
        case '+':
            return num1 + num2;
        case '-':
            return num1 - num2;
        case '*':
            return num1 * num2;
        case '/':
            return num1 / num2;
        case '^':
            return pow(num1, num2);
    }
    return 0;
}

double evaluate(string expression) {
    stack<double> operand_stack;
    stack<char> operator_stack;

    for (int i = 0; i < expression.length(); i++) {
        char token = expression[i];
        if (isdigit(token)) {
            double number = 0;
            while (i < expression.length() && isdigit(expression[i])) {
                number = number * 10 + (expression[i] - '0');
                i++;
            }
            i--;
            operand_stack.push(number);
        } else if (token == '(') {
            operator_stack.push(token);
        } else if (token == ')') {
            while (operator_stack.top() != '(') {
                char op = operator_stack.top();
                operator_stack.pop();
                double num2 = operand_stack.top();
                operand_stack.pop();
                double num1 = operand_stack.top();
                operand_stack.pop();
                operand_stack.push(calculate(num1, num2, op));
            }
            operator_stack.pop();
        } else if (token == '+' || token == '-' || token == '*' || token == '/' || token == '^') {
            while (!operator_stack.empty() && priority(operator_stack.top()) >= priority(token)) {
                char op = operator_stack.top();
                operator_stack.pop();
                double num2 = operand_stack.top();
                operand_stack.pop();
                double num1 = operand_stack.top();
                operand_stack.pop();
                operand_stack.push(calculate(num1, num2, op));
            }
            operator_stack.push(token);
        }
    }

    while (!operator_stack.empty()) {
        char op = operator_stack.top();
        operator_stack.pop();
        double num2 = operand_stack.top();
        operand_stack.pop();
        double num1 = operand_stack.top();
        operand_stack.pop();
        operand_stack.push(calculate(num1, num2, op));
    }

    return operand_stack.top();
}

int main() {
    string expression;
    cout << "请输入表达式（不含空格）：" << endl;
    cin >> expression;
    double result = evaluate(expression);
    cout << "表达式的值为：" << result << endl;
    return 0;
}

在上述代码中，`priority` 函数用于返回运算符的优先级，`calculate` 函数用于计算两个数字的运算结果，`evaluate` 函数用于对表达式进行求值，主函数中调用 `evaluate` 函数并输出结果。