C++ String: How to convert a numeric type to a string?

[Gabriel Fleseriu]

Q: How to convert a numeric type to a string?

A:

The old C method (deprecated):

char c[10];   // simply large enough - don't forget the 
              // extra byte needed for the trailing '\0' 
int i = 1234;
sprintf(c, "%d", i);

See 'sprintf()' in e.g. MSDN for further details.


Using 'CString':

int i = 1234;
CString cs;
cs.Format("%d", i);

The format specifiers are the same as for 'sprintf()'. See the 'CString' documentation in MSDN - it is fairly straight forward.

A word of warning: mismatching the format specifiers ('%d') and the actually passed parameters will lead to unpredictable results, both for 'sprintf()' and for 'CString::Format()'.


The C++ way:

Following sample shows a template function that uses Standard C++ classes to complete the task:

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

template <class T>
std::string to_string(T t, std::ios_base & (*f)(std::ios_base&))
{
  std::ostringstream oss;
  oss << f << t;
  return oss.str();
}

int main()
{
  // the second parameter of to_string() should be one of 
  // std::hex, std::dec or std::oct
  std::cout<<to_string<long>(123456, std::hex)<<std::endl;
  std::cout<<to_string<long>(123456, std::oct)<<std::endl;
  return 0;
} 

/* output:
1e240
361100
*/

This method is not only very elegant, but also type safe, because the compiler will pick the proper 'std::ostringstream::operator <<()' at compile time, according to the operand type.