#include <string>

#include <sstream>

struct str_stream

{

    std::stringstream & underlying_stream() const

    { return m_streamOut; }

    operator std::string() const

    {

        return m_streamOut.str();

    }

private:

    mutable std::stringstream m_streamOut;

};

template< class type>

    const str_stream & operator<< ( const str_stream & out, const type & value)

{

    out.underlying_stream() << value;

    return out;

}

int main()

{

    int nWordsCount;

    // ... calculate words count

    nWordsCount = 48;

    std::string str = str_stream() << "We have " << nWordsCount << " words";

    return 0;

}