Alternative to itoa() for converting integer to string C++?

Question

I was wonding if there was an alternative to itoa() for converting an integer to a string because when I run it in visual Studio I get warnings, and when I compile my program under Linux, it won't even compile.

Thanks,

tomek

Answer 1

boost::lexical_cast works pretty well.

#include <boost/lexical_cast.hpp>
int main(int argc, char** argv) {
    std::string foo = boost::lexical_cast<std::string>(argc);
}

Answer 2

Try sprintf():

char str[12];
int num = 3;
sprintf(str, "%d", num); // str now contains "3"

sprintf() is like printf() but outputs to a string.

Also, as Parappa mentioned in the comments, you might want to use snprintf() to stop a buffer overflow from occuring (where the number you're converting doesn't fit the size of your string.) It works like this:

snprintf(str, sizeof(str), "%d", num);

Answer 3

Allocate a string of sufficient length, then use snprintf.

Answer 4

Using C++ streams:

#include <sstream>

int i = 5;
std::string s;
std::stringstream out;
out << i;
s = out.str();

Taken from http://notfaq.wordpress.com/2006/08/30/c-convert-int-to-string/

Answer 5

Most of the above suggestions technically aren't C++, they're C solutions.

Look into the use of std::stringstream.

Answer 6

Behind the scenes, lexical_cast does this:

std::stringstream str;
str << myint;
std::string result;
str >> result;

If you don't want to "drag in" boost for this, then using the above is a good solution.

Answer 7

Note that all of the stringstream methods may involve locking around the use of the locale object for formatting. This may be something to be wary of if you're using this conversion from multiple threads...

See here for more. http://stackoverflow.com/questions/225362/convert-a-number-to-a-string-with-specified-length-in-c#226719

Answer 8

Archeology

itoa was a non-standard helper function designed to complement the atoi standard function, and probably hiding a sprintf (Most its features can be implemented in terms of sprintf): http://www.cplusplus.com/reference/clibrary/cstdlib/itoa.html

The C Way

Use sprintf. Or snprintf. Or whatever tool you find.

Despite the fact some functions are not in the standard, as rightly mentioned by "onebyone" in one of his comments, most compiler will offer you an alternative (e.g. Visual C++ has its own _snprintf you can typedef to snprintf if you need it).

The C++ way.

Use the C++ streams (in the current case std::stringstream (or even the deprecated std::strstream, as proposed by Herb Sutter in one of his books, because it's somewhat faster).

Conclusion

You're in C++, which means that you can choose the way you want it:

• The faster way (i.e. the C way), but you should be sure the code is a bottleneck in your application (premature optimizations are evil, etc.) and that your code is safely encapsulated to avoid risking buffer overruns.

• The safer way (i.e., the C++ way), if you know this part of the code is not critical, so better be sure this part of the code won't break at random moments because someone mistook a size or a pointer (which happens in real life, like... yesterday, on my computer, because someone thought it "cool" to use the faster way without really needing it).

Answer 9

On Windows CE derived platforms, there are no iostreams by default. The way to go there is preferaby with the _itoa<> family, usually _itow<> (since most string stuff are Unicode there anyway).

Answer 10

Try Boost.Format or FastFormat, both high-quality C++ libraries:

int i = 10;
std::string result;

WIth Boost.Format

result = str(boost::format("%1%", i));

or FastFormat

fastformat::fmt(result, "{0}", i);
fastformat::write(result, i);

Obviously they both do a lot more than a simple conversion of a single integer

Answer 11

I think that this all is too bad! I want to write my code and what I am doing the whole time is to find the best solution how to convert data types or something like that. I think all this should be done a long time ago. There must be a software engineer friendly language! There must be no need to build a new bicycle every time you write your code.

Answer 12

You can actually convert anything to a string with one cleverly written template function. This code example uses a loop to create subdirectories in a Win-32 system. The string concatenation operator, operator+, is used to concatenate a root with a suffix to generate directory names. The suffix is created by converting the loop control variable, i, to a C++ string, using the template function, and concatenating that with another string.

//Mark Renslow, Globe University, Minnesota School of Business, Utah Career College
//C++ instructor and Network Dean of Information Technology

#include <cstdlib>
#include <iostream>
#include <string>
#include <sstream> // string stream
#include <direct.h>

using namespace std;

string intToString(int x)
{
/**************************************/
/* This function is similar to itoa() */
/* "integer to alpha", a non-standard */
/* C language function. It takes an   */
/* integer as input and as output,    */
/* returns a C++ string.              */
/* itoa()  returned a C-string (null- */
/* terminated)                        */
/* This function is not needed because*/
/* the following template function    */
/* does it all                        */
/**************************************/   
       string r;
       stringstream s;

       s << x;
       r = s.str();

       return r;

}

template <class T>
string toString( T argument)
{
/**************************************/
/* This template shows the power of   */
/* C++ templates. This function will  */
/* convert anything to a string!      */
/* Precondition:                      */
/* operator<< is defined for type T    */
/**************************************/
       string r;
       stringstream s;

       s << argument;
       r = s.str();

       return r;

}

int main( )
{
    string s;

    cout << "What directory would you like me to make?";

    cin >> s;

    try
    {
      mkdir(s.c_str());
    }
    catch (exception& e) 
    {
      cerr << e.what( ) << endl;
    }

    chdir(s.c_str());

    //Using a loop and string concatenation to make several sub-directories
    for(int i = 0; i < 10; i++)
    {
        s = "Dir_";
        s = s + toString(i);
        mkdir(s.c_str());
    }
    system("PAUSE");
    return EXIT_SUCCESS;
}