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std::ref, std::cref

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< cpp‎ | utility‎ | functional

 
 
Utilidades de la biblioteca
Escriba apoyo (basic types, RTTI, type traits)
Gestión de memoria dinámica
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Programa de servicios públicos
Funciones variadic
Fecha y hora
Objetos Function
initializer_list(C++11)
bitset
hash(C++11)
Operadores relacionales
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Relational operators
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rel_ops::operator!=
rel_ops::operator>
rel_ops::operator<=
rel_ops::operator>=
Pares y tuplas
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Pairs and tuples
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pair
tuple(C++11)
piecewise_construct_t(C++11)
piecewise_construct(C++11)
Cambiar, hacia adelante y mover
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Swap, forward and move
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swap
forward(C++11)
move(C++11)
move_if_noexcept(C++11)
declval(C++11)
 
Objetos Function
Envoltorios de función
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Function wrappers
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function(C++11)
mem_fn(C++11)
bad_function_call(C++11)
Enlazar
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Bind
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bind(C++11)
is_bind_expression(C++11)
is_placeholder(C++11)
_1, _2, _3, ...(C++11)
Envolturas de referencia
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Reference wrappers
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reference_wrapper(C++11)
ref
cref
(C++11)
(C++11)
Envoltorios Operador
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Operator wrappers
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Negadores
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Negators
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Desaprobado aglutinantes y adaptadores
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Deprecated binders and adaptors
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unary_function(obsoleto)
binary_function(obsoleto)
ptr_fun(obsoleto)
pointer_to_unary_function(obsoleto)
pointer_to_binary_function(obsoleto)
mem_fun(obsoleto)
mem_fun_t
mem_fun1_t
const_mem_fun_t
const_mem_fun1_t
(obsoleto)
(obsoleto)
(obsoleto)
(obsoleto)
mem_fun_ref(obsoleto)
mem_fun_ref_t
mem_fun1_ref_t
const_mem_fun_ref_t
const_mem_fun1_ref_t
(obsoleto)
(obsoleto)
(obsoleto)
(obsoleto)
binder1st
binder2nd
(obsoleto)
(obsoleto)
bind1st
bind2nd
(obsoleto)
(obsoleto)
 
Defined in header <functional>
template< class T >
std::reference_wrapper<T> ref(T& t);
(1) (desde C++11)
template< class T >
std::reference_wrapper<T> ref( std::reference_wrapper<T> t );
(2) (desde C++11)
template< class T >
std::reference_wrapper<const T> cref( const T& t );
(3) (desde C++11)
template< class T >
std::reference_wrapper<const T> cref( std::reference_wrapper<T> t )
(4) (desde C++11)
Plantillas de función y ref cref son funciones auxiliares que generan un objeto de tipo std::reference_wrapper, con deducción argumento de plantilla para determinar el argumento de plantilla del resultado .
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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Contenido

[editar] Parámetros

t -
lvalue referencia al objeto que debe ser envuelto o una instancia 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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[editar] Valor de retorno

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

2) ref(t.get())

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

4) cref(t.get())

[editar] Excepciones

noexcept specification:  
noexcept
  (desde C++11)

[editar] Ejemplo

#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';
}

Output:

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

[editar] Ver también

CopyConstructible y CopyAssignable envoltura de referencia
Original:
CopyConstructible and CopyAssignable reference wrapper
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(clase de plantilla) [edit]