std::experimental::not_fn (3) - Linux Man Pages

std::experimental::not_fn: std::experimental::not_fn

NAME

std::experimental::not_fn - std::experimental::not_fn

Synopsis


Defined in header <experimental/functional>
template< class F> (library fundamentals TS v2)
/*unspecified*/ not_fn( F&& f );


Creates a forwarding call wrapper that returns the complement of the callable object it holds.

Parameters


f - the object from which the Callable object held by the wrapper is constructed

Return value


Let FD be std::decay_t<F> and fd be an lvalue of type FD constructed from std::forward<F>(f).
not_fn returns a forwarding call wrapper fn of unspecified type such that fn(a1, a2, ..., aN) is equivalent to !INVOKE(fd, a1, ..., aN), where INVOKE is the operation described in Callable.
The returned call wrapper is always MoveConstructible, and is CopyConstructible if FD is CopyConstructible.


Remarks


If fd is not Callable, or std::is_constructible<FD, F>::value is not true, the behavior is undefined.

Exceptions


Throws no exceptions, unless the construction of fd throws.

Possible implementation


  namespace detail {
      template<class F>
      struct not_fn_t {
          F f;
          template<class... Args>
          auto operator()(Args&&... args)
              noexcept(noexcept(!std::invoke(f, std::forward<Args>(args)...)))
              -> decltype(!std::invoke(f, std::forward<Args>(args)...)) {
              return !std::invoke(f, std::forward<Args>(args)...);
          }


          // cv-qualified overload for QoI
          template<class... Args>
          auto operator()(Args&&... args) const
              noexcept(noexcept(!std::invoke(f, std::forward<Args>(args)...)))
              -> decltype(!std::invoke(f, std::forward<Args>(args)...)) {
              return !std::invoke(f, std::forward<Args>(args)...);
          }


          template<class... Args>
          auto operator()(Args&&... args) volatile
              noexcept(noexcept(!std::invoke(f, std::forward<Args>(args)...)))
              -> decltype(!std::invoke(f, std::forward<Args>(args)...)) {
              return !std::invoke(f, std::forward<Args>(args)...);
          }
          template<class... Args>
          auto operator()(Args&&... args) const volatile
              noexcept(noexcept(!std::invoke(f, std::forward<Args>(args)...)))
              -> decltype(!std::invoke(f, std::forward<Args>(args)...)) {
              return !std::invoke(f, std::forward<Args>(args)...);
          }
      };
  }


  template<class F>
  detail::not_fn_t<std::decay_t<F>> not_fn(F&& f) { return { std::forward<F>(f) }; }

Notes


not_fn is intended to replace the C++03-era negators std::not1 and std::not2.

See also


not_fn Creates a function object that returns the complement of the result of the function object it holds
        (function template)
(C++17)