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std::ref, std::cref

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< cpp‎ | utility‎ | functional

 
 
 
Objets Function
Emballages de fonction
Original:
Function wrappers
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function (C++11)
mem_fn (C++11)
bad_function_call (C++11)
Lier
Original:
Bind
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bind (C++11)
is_bind_expression (C++11)
is_placeholder (C++11)
_1, _2, _3, ... (C++11)
Emballages de référence
Original:
Reference wrappers
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reference_wrapper (C++11)
ref
cref
(C++11)
(C++11)
Emballages opérateur
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Operator wrappers
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Négateurs
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Negators
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Obsolète liants et des adaptateurs
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Deprecated binders and adaptors
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unary_function (obsolète)
binary_function (obsolète)
ptr_fun (obsolète)
pointer_to_unary_function (obsolète)
pointer_to_binary_function (obsolète)
mem_fun (obsolète)
mem_fun_t
mem_fun1_t
const_mem_fun_t
const_mem_fun1_t
(obsolète)
(obsolète)
(obsolète)
(obsolète)
mem_fun_ref (obsolète)
mem_fun_ref_t
mem_fun1_ref_t
const_mem_fun_ref_t
const_mem_fun1_ref_t
(obsolète)
(obsolète)
(obsolète)
(obsolète)
binder1st
binder2nd
(obsolète)
(obsolète)
bind1st
bind2nd
(obsolète)
(obsolète)
 
Defined in header <functional>
template< class T >
std::reference_wrapper<T> ref(T& t);
(1) (depuis C++11)
template< class T >
std::reference_wrapper<T> ref( std::reference_wrapper<T> t );
(2) (depuis C++11)
template< class T >
std::reference_wrapper<const T> cref( const T& t );
(3) (depuis C++11)
template< class T >
std::reference_wrapper<const T> cref( std::reference_wrapper<T> t )
(4) (depuis C++11)
Modèles de fonction ref et cref sont des fonctions auxiliaires qui génèrent un objet de std::reference_wrapper type, en utilisant déduction argument de modèle pour déterminer l'argument template du résultat .
Original:
Function templates ref and cref are helper functions that generate an object of type std::reference_wrapper, using template argument deduction to determine the template argument of the result.
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Sommaire

[modifier] Paramètres

t -
référence lvalue à l'objet qui doit être enveloppé ou une instance de std::reference_wrapper
Original:
lvalue reference to object that needs to be wrapped or an instance of std::reference_wrapper
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[modifier] Retourne la valeur

1) std::reference_wrapper<T>(t)

2) ref(t.get())

3) std::reference_wrapper<const T>(t)

4) cref(t.get())

[modifier] Exeptions

noexcept specification:  
noexcept
   (depuis C++11)

[modifier] Exemple

#include <functional>
#include <iostream>
 
void f(int& n1, int& n2, const int& n3)
{
    std::cout << "In function: " << n1 << ' ' << n2 << ' ' << n3 << '\n';
    ++n1; // increments the copy of n1 stored in the function object
    ++n2; // increments the main()'s n2
    // ++n3; // compile error
}
 
int main()
{
    int n1 = 1, n2 = 2, n3 = 3;
    std::function<void()> bound_f = std::bind(f, n1, std::ref(n2), std::cref(n3));
    n1 = 10;
    n2 = 11;
    n3 = 12;
    std::cout << "Before function: " << n1 << ' ' << n2 << ' ' << n3 << '\n';
    bound_f();
    std::cout << "After function: " << n1 << ' ' << n2 << ' ' << n3 << '\n';
}

Résultat :

Before function: 10 11 12
In function: 1 11 12
After function: 10 12 12

[modifier] Voir aussi

adaptateur de référence respectant CopyConstructible et CopyAssignable
(classe générique) [edit]