How to concatenate a std::string and an int?

Question

I thought this would be really simple but it\'s presenting some difficulties. If I have

std::string name = \"John\";
int age = 21;

How do I

Answer 1

There are more options possible to use to concatenate integer (or other numerric object) with string. It is Boost.Format

#include 
#include 
int main()
{
    using boost::format;

    int age = 22;
    std::string str_age = str(format("age is %1%") % age);
}

and Karma from Boost.Spirit (v2)

#include 
#include 
#include 
int main()
{
    using namespace boost::spirit;

    int age = 22;
    std::string str_age("age is ");
    std::back_insert_iterator sink(str_age);
    karma::generate(sink, int_, age);

    return 0;
}

Boost.Spirit Karma claims to be one of the fastest option for integer to string conversion.