19 General utilities library [utilities]

19.14 Function objects [function.objects]

template<class F> unspecified not_fn(F&& f);

In the text that follows:

(1.1)
g is a value of the result of a not_fn invocation,
(1.2)
FD is the type decay_t<F>,
(1.3)
fd is the target object of g ([func.def]) of type FD, initialized with the initializer (std::forward<F>(f)) ([dcl.init]),
(1.4)
call_args is an argument pack used in a function call expression ([expr.call]) of g.

Mandates: is_constructible_v<FD, F> && is_move_constructible_v<FD> shall be true.

Expects: FD shall meet the requirements of Cpp17MoveConstructible.

Returns: A perfect forwarding call wrapper g with call pattern !invoke(fd, call_args...).

Throws: Any exception thrown by the initialization of fd.