设计一个可以进行四则运算，包括括号，小数点，表达式的c++程序

下面是一个可以进行四则运算的C++程序，支持括号、小数点、表达式等：

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

using namespace std;

bool isOperator(char ch) {
    return (ch == '+' || ch == '-' || ch == '*' || ch == '/');
}

int getPriority(char op) {
    if (op == '+' || op == '-') {
        return 1;
    } else if (op == '*' || op == '/') {
        return 2;
    } else {
        return 0;
    }
}

double applyOperator(double left, double right, char op) {
    switch (op) {
        case '+':
            return left + right;
        case '-':
            return left - right;
        case '*':
            return left * right;
        case '/':
            if (right == 0) {
                throw runtime_error("Divide by zero");
            }
            return left / right;
        default:
            throw invalid_argument("Invalid operator: " + string(1, op));
    }
}

double calculate(string expr) {
    stack<double> numStack;
    stack<char> opStack;
    int i = 0;
    bool isNegative = false;
    while (i < expr.length()) {
        char ch = expr[i];
        if (ch == ' ') {
            i++;
            continue;
        }
        if (ch == '-') {
            if (i == 0 || expr[i - 1] == '(') {
                isNegative = true;
                i++;
                continue;
            }
        }
        if (isdigit(ch) || ch == '.') {
            int j = i;
            while (j < expr.length() && (isdigit(expr[j]) || expr[j] == '.')) {
                j++;
            }
            string numStr = expr.substr(i, j - i);
            double num = stod(numStr);
            if (isNegative) {
                num = -num;
                isNegative = false;
            }
            numStack.push(num);
            i = j;
        } else if (ch == '(') {
            opStack.push(ch);
            i++;
        } else if (ch == ')') {
            while (!opStack.empty() && opStack.top() != '(') {
                char op = opStack.top();
                opStack.pop();
                double right = numStack.top();
                numStack.pop();
                double left = numStack.top();
                numStack.pop();
                double result = applyOperator(left, right, op);
                numStack.push(result);
            }
            if (!opStack.empty() && opStack.top() == '(') {
                opStack.pop();
            } else {
                throw invalid_argument("Unmatched parentheses");
            }
            i++;
        } else if (isOperator(ch)) {
            while (!opStack.empty() && getPriority(opStack.top()) >= getPriority(ch)) {
                char op = opStack.top();
                opStack.pop();
                double right = numStack.top();
                numStack.pop();
                double left = numStack.top();
                numStack.pop();
                double result = applyOperator(left, right, op);
                numStack.push(result);
            }
            opStack.push(ch);
            i++;
        } else {
            throw invalid_argument("Invalid character: " + string(1, ch));
        }
    }
    while (!opStack.empty()) {
        char op = opStack.top();
        opStack.pop();
        if (op == '(') {
            throw invalid_argument("Unmatched parentheses");
        }
        double right = numStack.top();
        numStack.pop();
        double left = numStack.top();
        numStack.pop();
        double result = applyOperator(left, right, op);
        numStack.push(result);
    }
    return numStack.top();
}

int main() {
    string expr = "2 * (3 + 4) - 5 / 2";
    try {
        double result = calculate(expr);
        cout << expr << " = " << result << endl;
    } catch (exception& e) {
        cerr << "Error: " << e.what() << endl;
    }

    return 0;
}

其中，`isOperator`函数用于判断一个字符是否为运算符；`getPriority`函数用于获取运算符的优先级；`applyOperator`函数用于计算两个数之间的运算结果；`calculate`函数用于计算一个表达式的值。这个程序使用两个栈分别存储数值和运算符，并根据运算符的优先级来进行计算。