Variadic TemplatesでBoost.Format拡張

かなり前に書いてから埋もれていたので、載せておきます。

サンプルコード

#include <iostream>
#include <cassert>
#include <shand/format.hpp>

int main()
{
    // variadic bind
    const std::string s1 = shand::format("%1% %2% %3%", "Hello", "World", 3.14).str();
    assert(s1 == "Hello World 3.14");

    // bind chain
    const std::string s2 = shand::format("%1% %2% %3%")("Hello")("World")(3.14).str();
    assert(s2 == "Hello World 3.14");

    // output stream
    std::cout << shand::format("%d %s", 123, "abc") << std::endl;

    // type-safe printf
    shand::print("%d %s\n", 123, "abc");

    // newline printf
    shand::println("%d %s", 123, "abc");
}

shand/format.hpp

#ifndef SHAND_FORMAT_INCLUDE
#define SHAND_FORMAT_INCLUDE

#include <boost/format.hpp>

namespace shand {

template <class CharT,
          class Traits = std::char_traits<CharT>,
          class Alloc = std::allocator<CharT> >
class basic_formatter {
public:
    typedef boost::basic_format<CharT, Traits, Alloc> format_type;
    typedef typename format_type::string_type         string_type;
    typedef basic_formatter&                          result_type;

    basic_formatter(const CharT* fmt) : fmt_(fmt) {}
    basic_formatter(const string_type& fmt) : fmt_(fmt) {}

    template <class T>
    basic_formatter& operator()(const T& arg)
    {
        fmt_ % arg;
        return *this;
    }

    string_type str() const
    {
        return fmt_.str();
    }

    template <class CharT2, class Traits2, class Alloc2>
    friend std::basic_ostream<CharT2, Traits2>&
        operator<<(std::basic_ostream<CharT2, Traits2>& os,
                   const basic_formatter<CharT2, Traits2, Alloc2>& fmt);

    template <class T>
    static basic_formatter& bind(basic_formatter& fmt, const T& x)
    {
        return fmt(x);
    }

    template <class Head, class... Tail>
    static basic_formatter& bind(basic_formatter& fmt, const Head& x, const Tail&... xs)
    {
        return bind(fmt(x), xs...);
    }

private:
    format_type fmt_;
};

typedef basic_formatter<char>       formatter;
typedef basic_formatter<wchar_t>    wformatter;

template <class CharT2, class Traits2, class Alloc2>
inline std::basic_ostream<CharT2, Traits2>&
    operator<<(std::basic_ostream<CharT2, Traits2>& os,
               const basic_formatter<CharT2, Traits2, Alloc2>& fmt)
{
    return os << fmt.fmt_;
}


template <class CharT, class Traits, class Alloc>
inline basic_formatter<CharT, Traits, Alloc>
    format(const std::basic_string<CharT, Traits, Alloc>& fmt)
{
    return basic_formatter<CharT, Traits, Alloc>(fmt);
}

template <class CharT, class Traits, class Alloc, class... Args>
inline basic_formatter<CharT, Traits, Alloc>
    format(const std::basic_string<CharT, Traits, Alloc>& fmt, const Args&... args)
{
    typedef basic_formatter<CharT, Traits, Alloc> format_type;
    format_type f(fmt);
    return format_type::bind(f, args...);
}

template <class CharT>
inline basic_formatter<CharT> format(const CharT* fmt)
{
    return basic_formatter<CharT>(fmt);
}

template <class CharT, class... Args>
inline basic_formatter<CharT> format(const CharT* fmt, const Args&... args)
{
    return format<CharT, std::char_traits<CharT>, std::allocator<CharT>, Args...>(fmt, args...);
}

template <class... Args>
inline void print(const std::string& fmt, const Args&... args)
{
    std::cout << format(fmt, args...);
}

template <class... Args>
inline void print(const std::wstring& fmt, const Args&... args)
{
    std::wcout << format(fmt, args...);
}

template <class CharT, class... Args>
inline void print(const CharT* fmt, const Args&... args)
{
    print(std::basic_string<CharT>(fmt), args...);
}

template <class... Args>
inline void println(const std::string& fmt, const Args&... args)
{
    std::cout << format(fmt, args...) << std::endl;
}

template <class... Args>
inline void println(const std::wstring& fmt, const Args&... args)
{
    std::wcout << format(fmt, args...) << std::endl;
}

template <class CharT, class... Args>
inline void println(const CharT* fmt, const Args&... args)
{
    println(std::basic_string<CharT>(fmt), args...);
}

} // namespace shand

#endif // SHAND_FORMAT_INCLUDE