Convert std::string to any numeric type

Asked Mar 27 '20 at 10:44

Active Mar 27 '20 at 10:50

Viewed 29 times

I want implement a function that convert std::string to any numeric type and I come with this

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

template<typename T>
T str2num(const std::string &str) {
    std::istringstream iss(str);
    T t;
    iss >> t;
    return t;
}

int main() {
    std::cout << str2num<uint64_t>("12345") << std::endl;
    std::cout << str2num<uint32_t>("12345") << std::endl;
    std::cout << str2num<uint16_t>("12345") << std::endl;
    std::cout << str2num<uint8_t>("123") << std::endl;
    return 0;
}

But not everything is fine.

The last line output 1 instead of 123.

Why did this happen and how to make it right?

edited Mar 27 '20 at 10:50

asked Mar 27 '20 at 10:44

xiaozhuai

1

https://en.cppreference.com/w/cpp/string/basic_string/stol – Matteo Ragni Mar 27 '20 at 10:49
also : [Why does int8_t and user input via cin shows strange result](https://stackoverflow.com/questions/24617889/why-does-int8-t-and-user-input-via-cin-shows-strange-result) – Sander De Dycker Mar 27 '20 at 10:51
OK, but how to made this function work? – xiaozhuai Mar 27 '20 at 10:55
You'll need to specialize the `uint8_t` case. – Eljay Mar 27 '20 at 11:12

Convert std::string to any numeric type

0 Answers0