How can I convert an int to a string in C++11 without using to_string or stoi?

Question

I know it sounds stupid, but I'm using MinGW32 on Windows7, and "to_string was not declared in this scope." It's an actual GCC Bug, and I've followed these instructions and they did not work. So, how can I convert an int to a string in C++11 without using to_string or stoi? (Also, I have the -std=c++11 flag enabled).

You could use `sprintf`. Actually there are a *lot* of options - `atoi` and company (not-quite-standard), string streams, the printf functions. — Panagiotis Kanavos, Jun 22 '15 at 07:18
@MattMcNabb the question is about formatting ints to strings, not parsing strings to ints — Panagiotis Kanavos, Jun 22 '15 at 07:20
`to_string` and `stoi` are the inverse of each other. Which is it you want to do? — kfsone, Jun 22 '15 at 07:20

score 9 · Accepted Answer · answered Jun 22 '15 at 07:21

Its not the fastest method but you can do this:

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

template<typename ValueType>
std::string stringulate(ValueType v)
{
    std::ostringstream oss;
    oss << v;
    return oss.str();
}

int main()
{
    std::cout << ("string value: " + stringulate(5.98)) << '\n';
}

score 4 · Answer 2 · answered Jun 22 '15 at 07:43

4

I'd like to answer it differently: just get mingw-w64.

Seriously, MinGW32 is just so full of issues it's not even funny:

With MinGW-w64 you get for free:

support for Windows Unicode entry point (wmain/wWinMain)
better C99 support
better C++11 support (as you see in your question!)
large file support
support for C++11 threads
support for Windows 64 bit
cross compiling! so you can work on your Windows app on your favorite platform.

answered Jun 22 '15 at 07:43

rr-

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As of MinGW-w64 4.9.2, C++14 is also supported (and C11 too IIRC). – Chnossos Jun 22 '15 at 08:13
Ok, you've convinced me haha.. I'll uninstall it and download mingw-w64. – Ericson Willians Jun 22 '15 at 08:19

Ziming Song · Answer 3 · 2015-06-22T07:28:17.957

2

You can use stringstream.

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

int main() {
    int num = 12345;
    stringstream ss;
    ss << num;
    string str;
    ss >> str;
    cout << str << endl;
    return 0;
}

edited Jun 22 '15 at 07:28

answered Jun 22 '15 at 07:18

Ziming Song

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score 1 · Answer 4 · answered Jun 22 '15 at 07:21

1

You could roll your own function to do it.

std::string convert_int_to_string (int x) {
  if ( x < 0 )
    return std::string("-") + convert_int_to_string(-x);
  if ( x < 10 )
    return std::string(1, x + '0');
  return convert_int_to_string(x/10) + convert_int_to_string(x%10);
}

answered Jun 22 '15 at 07:21

Jay Bosamiya

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2

"You could" != "You should". Just pointing out one other possible thing. – Jay Bosamiya Jun 22 '15 at 07:24

score 1 · Answer 5 · answered Feb 25 '18 at 19:50

1

Despite the fact that previous answers are better I want to give you another possibility to implement an INT to STRING method following the next old school code:

#include <string>

std::string int2string(int value) {
    char buffer[20]; // Max num of digits for 64 bit number
    sprintf(buffer,"%d", value);
    return std::string(buffer);
}

answered Feb 25 '18 at 19:50

omotto

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Will cause a buffer overflow on a system with 64-bit ints – M.M Feb 25 '18 at 19:57
Nop, beacuse 64bit needs 19 digits (in the example there are 20 digit buffer) 9,223,372,036,854,775,807 (19 digits) – omotto Feb 25 '18 at 20:09
You forgot about the minus sign – M.M Feb 25 '18 at 20:19
Nop, because buffer has 20 bytes for 19 digits (1 byte extra for sign) – omotto Feb 26 '18 at 11:31
You forgot about the null terminator – M.M Feb 26 '18 at 20:05

How can I convert an int to a string in C++11 without using to_string or stoi?

5 Answers5