templateパラメータによる文字リテラルの変換

cpp_template_literal.cpp

#include <iostream>
#include <string>
#include <tuple>

#include <boost/preprocessor/cat.hpp>

#define literal_cast(T, CHARS)   \
  std::get<const T*>(            \
    std::tuple<                  \
      const char*,               \
      const wchar_t*             \
  >(                             \
      CHARS,                     \
      BOOST_PP_CAT(L, CHARS)     \
  ))

template <typename CharT>
void trim(std::basic_string<CharT> &s, const CharT *chars = literal_cast(CharT, " \r\n\t\v"))
{
  s.erase(0, s.find_first_not_of(chars));
  s.erase(s.find_last_not_of(chars)+1);
}

int main()
{
  {
    std::string str{ "  ABC  " };
    trim(str);
    std::cout << str << std::endl;
  }
  {
    std::wstring wstr{ L"  ABC  " };
    trim(wstr);
    std::wcout << wstr << std::endl;
  }
}