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std::ref, std::cref

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Os operadores relacionais
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rel_ops::operator!=
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Invólucros de referência
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reference_wrapper(C++11)
ref
cref
(C++11)
(C++11)
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Negators
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unary_function(obsoleta)
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(obsoleta)
 
Defined in header <functional>
template< class T >
std::reference_wrapper<T> ref(T& t);
(1) (a partir do C++ 11)
template< class T >
std::reference_wrapper<T> ref( std::reference_wrapper<T> t );
(2) (a partir do C++ 11)
template< class T >
std::reference_wrapper<const T> cref( const T& t );
(3) (a partir do C++ 11)
template< class T >
std::reference_wrapper<const T> cref( std::reference_wrapper<T> t )
(4) (a partir do C++ 11)
Modelos de função ref e cref são funções auxiliares que geram um objeto de std::reference_wrapper tipo, usando a dedução argumento de modelo para determinar o argumento de modelo do 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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Índice

[editar] Parâmetros

t -
lvalue referência ao objeto que precisa ser embrulhada ou uma instância 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] Exceções

noexcept specification:  
noexcept
  (a partir do C++ 11)

[editar] Exemplo

#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] Veja também

CopyConstructible e CopyAssignable invólucro de referência
Original:
CopyConstructible and CopyAssignable reference wrapper
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(modelo de classe) [edit]