19 General utilities library [utilities]

19.14 Function objects [function.objects]

19.14.14 Polymorphic function wrappers [func.wrap]

19.14.14.2 Class template function [func.wrap.func]

19.14.14.2.6 Null pointer comparison functions [func.wrap.func.nullptr]

template<class R, class... ArgTypes> bool operator==(const function<R(ArgTypes...)>& f, nullptr_t) noexcept; template<class R, class... ArgTypes> bool operator==(nullptr_t, const function<R(ArgTypes...)>& f) noexcept;
Returns: !f.
template<class R, class... ArgTypes> bool operator!=(const function<R(ArgTypes...)>& f, nullptr_t) noexcept; template<class R, class... ArgTypes> bool operator!=(nullptr_t, const function<R(ArgTypes...)>& f) noexcept;
Returns: (bool)f.