Maybe sane string formatting in C++11?

formatter.cpp

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

using StringCIter_t = std::string::const_iterator;

// This is the base case we don't like, how 
inline StringCIter_t real_format(const std::string& fmt, std::stringstream& stream)
{
    throw std::runtime_error("Too few arguments provided to formatter!");
    stream << fmt;
    return fmt.cend();
}

template<typename T>
StringCIter_t real_format(const std::string& fmt, std::stringstream& stream, T arg)
{
    StringCIter_t cit = fmt.cbegin();

    while(cit != fmt.cend())
    {
        if(*cit == '{')
        {
            StringCIter_t::value_type c = *cit;
            ++cit;
            // Found somewhere to insert the arg
            if(*cit == '}')
            {
                stream << arg;
                ++cit;
                break;
            }
            else
            {
                stream << c << *cit;
            }
        }
        else
        {
            stream << *cit;
            ++cit;
        }
    }

    return cit;
}

template<typename T, typename... Ts>
inline StringCIter_t real_format(const std::string& fmt,
                   std::stringstream& stream, T arg, Ts... rest)
{
    StringCIter_t cit = real_format(fmt, stream, arg);
    return real_format(std::string(cit, fmt.cend()), stream, rest...);
}

template<typename T, typename... Ts>
inline std::string format(const std::string& fmt, T arg, Ts... rest)
{
    std::stringstream stream_;
    real_format(fmt, stream_, arg, rest...);
    return stream_.str();
}

template<typename T>
inline std::string format(const std::string& fmt, T arg)
{
    std::stringstream stream_;
    StringCIter_t cit = real_format(fmt, stream_, arg);
    if(fmt.cend() != cit)
    {
        real_format(std::string(cit, fmt.cend()), stream_);
    }
    return stream_.str();
}
int main()
{
    // This should throw a std::runtime_error
    // std::cout << format("Hello, {}, {}!", "World") << std::endl;
    // This should print `Hello, World, C++ number 1!`
    std::cout << format("Hello, {}, C++ number {}!", "World", 1) << std::endl;
    return 0;
}