Thread: opposite to atoi.

Originally Posted by Mark S.

I know that the atoi() function converts a string number to an int equivalent.

Is there a similar function that converts an int number to a string number.

Thanks

Mark S.

Yep, they're called stringstreams, and they work both ways. There is also a non-standard function known as itoa(), but forget about that. Also, forget about atoi() while you're at it unless you're interested in C. The C++ way is stringstreams.

The C pendant to atoi is sprintf. But for C++, stick with the streams or lexical_cast.

>I know that the atoi() function converts a string number to an int equivalent.
That's the theory behind atoi. If you're wise you'll forget it exists. In C it has awful error handling semantics, and strtol (or even sscanf) is the recommended alternative. In C++ there are much better and safer ways to do this (such as stringstreams or the lovely boost::lexical_cast) that are consistent in both directions, unlike the C solution.

>Here's a nice example that Prelude used the other day to put a number into a string
It's only slightly more complicated and vastly more useful to generalize:

Code:

#include <sstream>
#include <typeinfo>

namespace jsw {
  template <typename T, typename U>
  T lexical_cast ( U src )
  {
    std::stringstream s;
    T dst;

    if ( !( s << src ) || !( s >> dst ) )
      throw std::bad_cast ( "Invalid conversion" );

    return dst;
  }
}

Of course, that's nothing more than a simplified version of what boost::lexical_cast does.

I think there's an itoa() function, unless I'm making that up, but I don't think I am.

If you compile as ANSI-compatible, then your compiler will complain that you are. It's a non-standard function, although cppreference.com has it.