5장. RHEL 10에서 주요 변경 사항

#pragma GCC diagnostic push
#pragma GCC diagnostic ignored “-Wdeprecated-declarations"
class Functor : public std::unary_function<int, int>
{ /* … */ };
#pragma GCC diagnostic pop

class Functor
{
  using result_type = int;
  using argument_type = int;
  /* … */
};