Function objects | |
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| (until C++17*)(until C++17*) | (until C++17*)(until C++17*) |
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R operator()( Args...args)/*cv*//*ref*/noexcept(/*noex*/); | | (since C++23) |
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Invokes the stored callable target with the parametersargs. The/*cv*/,/*ref*/, and/*noex*/ parts ofoperator() are identical to those of the template parameter ofstd::move_only_function.
Equivalent toreturnstd::invoke_r<R>(/*cv-ref-cast*/(f),std::forward<Args>(args)...);, wheref is a cv-unqualified lvalue that denotes the target object of*this, and/*cv-ref-cast*/(f) is equivalent to:
- f ifcvref is either empty or&, or
- std::as_const(f) ifcvref is eitherconst orconst&, or
- std::move(f) ifcvref is&&, or
- std::move(std::as_const(f)) ifcvref isconst&&.
The behavior is undefined if*this is empty.
[edit]Parameters
| args | - | parameters to pass to the stored callable target |
[edit]Return value
std::invoke_r<R>(/*cv-ref-cast*/(f),std::forward<Args>(args)...).
[edit]Exceptions
Propagates the exception thrown by the underlying function call.
[edit]Example
The following example shows howstd::move_only_function can passed to other functions by value. Also, it shows howstd::move_only_function can store lambdas.
#include <iostream>#include <functional> void call(std::move_only_function<int()const> f)// can be passed by value{std::cout<< f()<<'\n';} int normal_function(){return42;} int main(){int n=1;auto lambda=[&n](){return n;};std::move_only_function<int()const> f= lambda; call(std::move(f)); n=2; call(lambda); f= normal_function; call(std::move(f));}Output:
[edit]See also
| invokes the target
(public member function ofstd::function<R(Args...)>)[edit] |
| calls the stored function
(public member function ofstd::reference_wrapper<T>)[edit] |
| invokes anyCallable object with given argumentsand possibility to specify return type(since C++23)
(function template)[edit] |
