deduction guides for std::function
Defined in header <functional> |
||
---|---|---|
template< class R, class... ArgTypes > function( R(*)(ArgTypes...) ) -> function<R(ArgTypes...)>; |
(1) | (since C++17) |
template< class F > function( F ) -> function</*see below*/>; |
(2) | (since C++17) |
2) This overload participates in overload resolution only if
&F::operator()
is well-formed when treated as an unevaluated operand and
decltype(&F::operator())
is of the form
R(G::*)(A...)
(optionally cv-qualified, optionally noexcept, optionally lvalue reference qualified) for some class type G. The deduced type is
std::function<R(A...)>
.
Notes
The type deduced by these deduction guides may change in a later standard revision (in particular, this might happen if noexcept
support is added to std::function
in a later standard).
Example
#include <functional> int func(double) { return 0; } int main() { std::function f{func}; // guide #1 deduces function<int(double)> int i = 5; std::function g = [&](double) { return i; }; // guide #2 deduces function<int(double)> }
Defect reports
The following behavior-changing defect reports were applied retroactively to previously published C++ standards.
DR | Applied to | Behavior as published | Correct behavior |
---|---|---|---|
LWG 3238 | C++17 | behavior of (2) was unclear | clarified |
© cppreference.com
Licensed under the Creative Commons Attribution-ShareAlike Unported License v3.0.
https://en.cppreference.com/w/cpp/utility/functional/function/deduction_guides