20 General utilities library [utilities]

20.9 Function objects [function.objects]

20.9.11 Polymorphic function wrappers [func.wrap]

20.9.11.2 Class template function [func.wrap.func]

20.9.11.2.6 null pointer comparison operators [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;

1

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;

2

Returns: (bool) f.