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]

20.9.11.2.3 function capacity [func.wrap.func.cap]

explicit operator bool() const noexcept;

1

Returns: true if *this has a target, otherwise false.