[c++] c++ parse int from string

Possible Duplicate:
How to parse a string to an int in C++?

I have done some research and some people say to use atio and others say it's bad, and I can't get it to work anyways.

So I just want to ask flat out, whats the right way to convert a string to a int.

string s = "10";
int i = s....?

Thanks!

You can use istringstream.

string s = "10";

// create an input stream with your string.
istringstream is(str);

int i;
// use is like an input stream
is >> i;

Some handy quick functions (if you're not using Boost):

template<typename T>
std::string ToString(const T& v)
{
    std::ostringstream ss;
    ss << v;
    return ss.str();
}

template<typename T>
T FromString(const std::string& str)
{
    std::istringstream ss(str);
    T ret;
    ss >> ret;
    return ret;
}

Example:

int i = FromString<int>(s);
std::string str = ToString(i);

Works for any streamable types (floats etc). You'll need to #include <sstream> and possibly also #include <string>.

You can use boost::lexical_cast:

#include <iostream>
#include <boost/lexical_cast.hpp>

int main( int argc, char* argv[] ){
std::string s1 = "10";
std::string s2 = "abc";
int i;

   try   {
      i = boost::lexical_cast<int>( s1 );
   }
   catch( boost::bad_lexical_cast & e ){
      std::cout << "Exception caught : " << e.what() << std::endl;
   }

   try   {
      i = boost::lexical_cast<int>( s2 );
   }
   catch( boost::bad_lexical_cast & e ){
      std::cout << "Exception caught : " << e.what() << std::endl;
   }

   return 0;
}

There is no "right way". If you want a universal (but suboptimal) solution you can use a boost::lexical cast.

A common solution for C++ is to use std::ostream and << operator. You can use a stringstream and stringstream::str() method for conversion to string.

If you really require a fast mechanism (remember the 20/80 rule) you can look for a "dedicated" solution like C++ String Toolkit Library

Best Regards,
Marcin