翻译强力驱动How can we convert u32string to int in C++11?
Additional, what method should I use to convert part of such string to int - lets say having begin and end iterator available?
I've tried:
u32string test=U"14"; cout << atoi(test.c_str());but it throws:
candidate function not viable: no known conversion from 'const char32_t *' to 'const char *' for 1st argument extern int atoi (__const char *__nptr)#include <locale> // wstring_convert #include <codecvt> // codecvt_utf8 #include <iostream> // cout #include <string> // stoi and u32string int main() { std::wstring_convert<std::codecvt_utf8<char32_t>, char32_t> convert; std::u32string str = U"14"; std::cout << std::stoi(convert.to_bytes(str)); }This depends on UTF-8 and the "C" locale using the same representation for digits.
GCC's standard library implementation libstdc++ does not include the codecvt header or std::wstring_convert yet. libc++ does include both of these, as does Visual Studio's standard library implementation. If you have to use libstdc++ you may find it easiest to just implement a simple conversion function yourself.
#include <algorithm> // transform #include <iterator> // begin, end, and back_inserter std::string u32_to_ascii(std::u32string const &s) { std::string out; std::transform(begin(s), end(s), back_inserter(out), [](char32_t c) { return c < 128 ? static_cast<char>(c) : '?'; }); return out; } int u32toi(std::u32string const &s) { return stoi(u32_to_ascii(s)); }Edited because my first answer was stupid.
Here is what i managed to do, however its probably not very efficient, and it assumes your string is valid.
#include <string> #include <iostream> int main() { std::u32string str = U"14"; std::string res; for (auto c = str.begin(); c != str.end(); ++c) { char t = *c; res.push_back(t); } std::cout << "\nVal = " << atoi(res.c_str()) << std::endl; return (0); }