Method operator()

extlibs/fmt/include/fmt/printf.h:82–84

      : arg_(arg), type_(type) {}

  void operator()(bool value) {
    if (type_ != 's') operator()<bool>(value);
  }

  template <typename U, FMT_ENABLE_IF(std::is_integral<U>::value)>
  void operator()(U value) {