Difference between revisions of "cpp/utility/functional/not fn"
From cppreference.com
< cpp | utility | functional
m (Text replace - "par req concept" to "par req named") |
m (link to ja) |
||
| Line 112: | Line 112: | ||
{{dsc end}} | {{dsc end}} | ||
| − | {{langlinks|zh}} | + | {{langlinks|ja|zh}} |
Revision as of 08:39, 6 July 2018
| Defined in header <functional>
|
||
| template< class F> /*unspecified*/ not_fn( F&& f ); |
(since C++17) | |
Creates a forwarding call wrapper that returns the negation of the callable object it holds.
Contents |
Parameters
| f | - | the object from which the Callable object held by the wrapper is constructed |
| Type requirements | ||
-std::decay_t<F> must meet the requirements of Callable and MoveConstructible.
| ||
| -std::is_constructible_v<std::decay_t<F>, F> is required to be true | ||
Return value
A function object of unspecified type T. It has the following members:
std::not_fn return type
Member objects
The return type of std::not_fn holds a member object of type std::decay_t<F>.
Constructors
| explicit T(F&& f); |
(1) | |
| T(T&& f) = default; T(const T& f) = default; |
(2) | |
1) The constructor initializes the member object (of type std::decay_t<F>) from std::forward<F>(f). Throws any exception thrown by the constructor selected
2) Because std::decay_t<F> is required to be MoveConstructible, the returned call wrapper is always MoveConstructible, and is CopyConstructible if std::decay_t<F> is CopyConstructible.
Member function operator()
| template<class... Args> auto operator()(Args&&... args) & -> decltype(!std::declval<std::invoke_result_t<std::decay_t<F>&, Args...>>()); |
(1) | |
| template<class... Args> auto operator()(Args&&... args) && -> decltype(!std::declval<std::invoke_result_t<std::decay_t<F>, Args...>>()); |
(2) | |
1) Equivalent to return !std::invoke(fd, std::forward<Args>(args)...)
2) Equivalent to return !std::invoke(std::move(fd), std::forward<Args>(args)...)
where fd is the member object of type std::decay_t<F>
Exceptions
Throws no exceptions, unless the construction of fd throws.
Notes
not_fn is intended to replace the C++03-era negators std::not1 and std::not2.
See also
| (deprecated in C++17)(removed in C++20) |
constructs custom std::unary_negate object (function template) |
| (deprecated in C++17)(removed in C++20) |
constructs custom std::binary_negate object (function template) |
