|
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Old binders and adaptors | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Defined in header <functional> | ||
template<class F,class...Args> std::invoke_result_t<F, Args...> | (1) | (since C++17) (constexpr since C++20) |
template<class R,class F,class...Args> constexpr R | (2) | (since C++23) |
INVOKE(std::forward<F>(f),std::forward<Args>(args)...). This overload participates in overload resolution only ifstd::is_invocable_v<F, Args...> istrue.INVOKE<R>(std::forward<F>(f),std::forward<Args>(args)...). This overload participates in overload resolution only ifstd::is_invocable_r_v<R, F, Args...> istrue.Contents |
| f | - | Callable object to be invoked |
| args | - | arguments to pass tof |
R, ifR is not (possiblycv-qualified)void. None otherwise.| invoke (1) |
|---|
namespace detail{template<class>constexprbool is_reference_wrapper_v=false;template<class U>constexprbool is_reference_wrapper_v<std::reference_wrapper<U>>=true; template<class T>using remove_cvref_t=std::remove_cv_t<std::remove_reference_t<T>>; template<class C,class Pointed,class Object,class...Args>constexpr decltype(auto) invoke_memptr(Pointed C::* member, Object&& object, Args&&...args){using object_t= remove_cvref_t<Object>;constexprbool is_member_function=std::is_function_v<Pointed>;constexprbool is_wrapped= is_reference_wrapper_v<object_t>;constexprbool is_derived_object=std::is_same_v<C, object_t>||std::is_base_of_v<C, object_t>; ifconstexpr(is_member_function){ifconstexpr(is_derived_object)return(std::forward<Object>(object) .* member)(std::forward<Args>(args)...);elseifconstexpr(is_wrapped)return(object.get() .* member)(std::forward<Args>(args)...);elsereturn((*std::forward<Object>(object)) .* member)(std::forward<Args>(args)...);}else{ static_assert(std::is_object_v<Pointed>&& sizeof...(args)==0);ifconstexpr(is_derived_object)returnstd::forward<Object>(object) .* member;elseifconstexpr(is_wrapped)return object.get() .* member;elsereturn(*std::forward<Object>(object)) .* member;}}}// namespace detail template<class F,class...Args>constexprstd::invoke_result_t<F, Args...> invoke(F&& f, Args&&...args)noexcept(std::is_nothrow_invocable_v<F, Args...>){ifconstexpr(std::is_member_pointer_v<detail::remove_cvref_t<F>>)return detail::invoke_memptr(f,std::forward<Args>(args)...);elsereturnstd::forward<F>(f)(std::forward<Args>(args)...);} |
| invoke_r (2) |
template<class R,class F,class...Args> requiresstd::is_invocable_r_v<R, F, Args...>constexpr R invoke_r(F&& f, Args&&...args)noexcept(std::is_nothrow_invocable_r_v<R, F, Args...>){ifconstexpr(std::is_void_v<R>) std::invoke(std::forward<F>(f),std::forward<Args>(args)...);elsereturn std::invoke(std::forward<F>(f),std::forward<Args>(args)...);} |
| Feature-test macro | Value | Std | Feature |
|---|---|---|---|
__cpp_lib_invoke | 201411L | (C++17) | std::invoke,(1) |
__cpp_lib_invoke_r | 202106L | (C++23) | std::invoke_r,(2) |
#include <functional>#include <iostream>#include <type_traits> struct Foo{ Foo(int num): num_(num){}void print_add(int i)const{std::cout<< num_+ i<<'\n';}int num_;}; void print_num(int i){std::cout<< i<<'\n';} struct PrintNum{void operator()(int i)const{std::cout<< i<<'\n';}}; int main(){std::cout<<"invoke a free function: "; std::invoke(print_num,-9); std::cout<<"invoke a lambda: "; std::invoke([](){ print_num(42);}); std::cout<<"invoke a member function: ";const Foo foo(314159); std::invoke(&Foo::print_add, foo,1); std::cout<<"invoke (i.e., access) a data member num_: "<< std::invoke(&Foo::num_, foo)<<'\n'; std::cout<<"invoke a function object: "; std::invoke(PrintNum(),18); #if defined(__cpp_lib_invoke_r)auto add=[](int x,int y){return x+ y;};std::cout<<"invoke a lambda converting result to float: ";auto ret= std::invoke_r<float>(add,11,22); static_assert(std::is_same<decltype(ret),float>());std::cout<<std::fixed<< ret<<"\ninvoke print_num: "; std::invoke_r<void>(print_num,44);#endif}
Possible output:
invoke a free function: -9invoke a lambda: 42invoke a member function: 314160invoke (i.e., access) a data member num_: 314159invoke a function object: 18invoke a lambda converting result to float: 33.000000invoke print_num: 44
(C++11) | creates a function object out of a pointer to a member (function template)[edit] |
(C++11)(removed in C++20)(C++17) | deduces the result type of invoking a callable object with a set of arguments (class template)[edit] |
| checks if a type can be invoked (as if bystd::invoke) with the given argument types (class template)[edit] | |
(C++17) | calls a function with a tuple of arguments (function template)[edit] |
