c++ - 使用 stod() 在小数点后转换带有字母的字符串时没有异常

Question

#include<iostream>
#include<string>
using namespace std;

int main()
{
    double var;
    string word("20.njhggh");
    var = stod(word);
    cout << var << endl;
    return 0;
}

输出是:20

stod 函数不会抛出输入 "20.njhggh" 的异常。它只是忽略小数点后的字母。对于上述情况，我如何抛出异常

Answer 1

How do I trow exception for the above case

根据文档，stod 有第二个参数:

double      stod( const std::string& str, std::size_t* pos = 0 );

If pos is not a null pointer, then a pointer ptr, internal to the conversion functions, will receive the address of the first unconverted character in str.c_str(), and the index of that character will be calculated and stored in *pos, giving the number of characters that were processed by the conversion.

因此，如果您想在某些字符串未用于转换时抛出异常，您可以将 *pos 与字符串的大小进行比较:

std::size_t pos;
var = stod(word, &pos);
if (pos < word.size())
    throw some_exception();