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Defined in header <functional> | ||
template<class...> class copyable_function;// not defined | (1) | (since C++26) |
template<class R,class...Args> class copyable_function<R(Args...)>; | (2) | (since C++26) |
Class templatestd::copyable_function is a general-purpose polymorphic function wrapper.std::copyable_function objects can store and invoke anyCopyConstructibleCallabletarget — functions,lambda expressions,bind expressions, or other function objects, as well as pointers to member functions and pointers to member objects.
The stored callable object is called thetarget ofstd::copyable_function. If astd::copyable_function contains no target, it is calledempty. Unlikestd::function, invoking anemptystd::copyable_function results in undefined behavior.
std::copyable_functions supports every possible combination ofcv-qualifiers (not includingvolatile),ref-qualifiers, andnoexcept-specifiers provided in its template parameter. These qualifiers and specifier (if any) are added to itsoperator().
std::copyable_function satisfies the requirements ofCopyConstructible andCopyAssignable.
Contents |
| Type | Definition |
result_type | R |
constructs a newstd::copyable_function object(public member function)[edit] | |
destroys astd::copyable_function object(public member function)[edit] | |
| replaces or destroys the target (public member function)[edit] | |
swaps the targets of twostd::copyable_function objects(public member function)[edit] | |
checks if thestd::copyable_function has a target(public member function)[edit] | |
| invokes the target (public member function)[edit] |
(C++26) | overloads thestd::swap algorithm (function)[edit] |
(C++26) | compares astd::copyable_function withnullptr(function)[edit] |
Implementations may store a callable object of small size within thestd::copyable_function object. Such small object optimization is effectively required for function pointers andstd::reference_wrapper specializations, and can only be applied to typesT for whichstd::is_nothrow_move_constructible_v<T> istrue.
| Feature-test macro | Value | Std | Feature |
|---|---|---|---|
__cpp_lib_copyable_function | 202306L | (C++26) | std::copyable_function |
| This section is incomplete Reason: no example |
(C++11) | copyable wrapper of any copy constructible callable object (class template)[edit] |
(C++23) | move-only wrapper of any callable object that supports qualifiers in a given call signature (class template)[edit] |
(C++26) | non-owning wrapper of any callable object (class template)[edit] |
