从未执行的函数中抛出异常

Question

不明白为什么在逐行调试的时候连函数都不进入就一直抛异常

我的代码：

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

#define LENGTH 10

using namespace std;

bool is_number(const std::string& s)
{
    try
    {
        std::stod(s);
    }
    catch (...)
    {
        return false;
    }
    return true;
}

int countAfterComma(double num) {
    stringstream s;
    s << num;
    int pos = s.str().find('.');
    if (pos != string::npos) return s.str().size() - 1 - pos;
    return 0;
}

int countBeforeComma(double num) {
    string str = to_string(num);
    int count = 0;
    while (str[count] != '.') count++;
    return count;
}

double calcOpz(string opz, stack <double> Buff) {
    int length = opz.length();

    string lexems[LENGTH];
    int j = 0;
    for (int i = 0; i < length; i++) {
        if (opz[i] != ' ')
            lexems[j] += opz[i];
        else j++;
    }

    for (int i = 0; i < j + 1; i++) {
        if (is_number(lexems[i])) Buff.push(stod(lexems[i]));
        else {
            double num1 = Buff.top();
            Buff.pop();
            double num2 = Buff.top();
            Buff.pop();
            if (lexems[i] == "+") Buff.push(num1 + num2);
            else if (lexems[i] == "-") Buff.push(num2 - num1);
            else if (lexems[i] == "*") Buff.push(num1 * num2);
            else if (lexems[i] == "^") {
                if (floor(num1) != num1) {
                    if (num2 < 0) throw "Your base num less than zero";
                    //int test = countBeforeComma(num1);
                    int _comma = countAfterComma(num1);
                    int numerator = num1 * pow(10, _comma);
                    int denominator = pow(10, _comma + countBeforeComma(num1));
                    Buff.push(pow(pow(num2, 1.0 / denominator), numerator));
                }
                else {
                    Buff.push(pow(num2, num1));
                }
            }
            else Buff.push(num2 / num1);
        }
    }

    return Buff.top();
}

int main()
{
    stack<double> buff;
    cout << calcOpz("-2 1.5 ^", buff);
}

它发生在这条注释行上：

int _comma = countAfterComma(num1);

Visual Studio 警告我错误代码：

C4244 (https://docs.microsoft.com/en-us/cpp/error-messages/compiler-warnings/compiler-warning-level-2-c4244?view=msvc-160).

Answer 1

[...] it does not even enter the function.

确实如此，因为num2 = -2，字符串"Your base num less than zero"被抛出但没有被捕获，不推荐抛出字符串。我建议你将它包装在一个实际的异常中并抛出它。

条件如下：

if (lexems[i] == "+") Buff.push(num1 + num2);               // false
else if (lexems[i] == "-") Buff.push(num2 - num1);          // false
else if (lexems[i] == "*") Buff.push(num1 * num2);          // false
else if (lexems[i] == "^") {                                // true
    if (floor(num1) != num1) {                              // true
        if (num2 < 0) throw "Your base num less than zero"; // true

将投掷线更改为：

if (num2 < 0) throw invalid_argument("Your base num less than zero");

并在 main 中捕获它：

int main()
{
    stack<double> buff;
    string str = "-2 1.5 ^";

    try {
        cout << calcOpz(str, buff);
    }
    catch (exception& e)
    {
        cout << e.what(); // or whatever you need to do
    }
}

会使问题明显。

Live demo

Visual Studio 实际上有一些非常好的通用调试功能，好坏取决于你的版本，好好利用它。

从未执行的函数中抛出异常

Exception being thrown from function that is not being executed

c++

function

converters

throw

pow