std::placeholders::_1, std::placeholders::_2, ..., std::placeholders::_N

 

C++

Idioma

Conceptos

Utilidades de la biblioteca

Strings biblioteca

Contenedores biblioteca

Algoritmos biblioteca

Los iteradores biblioteca

Numéricos biblioteca

Entrada / salida de la biblioteca

Localizaciones biblioteca

Expresiones biblioteca Regular (C++11)

Operaciones de biblioteca Atómica (C++11)

Tema Biblioteca de ayuda (C++11)

 

Utilidades de la biblioteca

Escriba apoyo (basic types, RTTI, type traits)

Gestión de memoria dinámica

Gestión de errores

Programa de servicios públicos

Funciones variadic

Fecha y hora

Objetos Function

initializer_list (C++11)

bitset

hash (C++11)

Operadores relacionales Original: Relational operators The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.

rel_ops::operator!= rel_ops::operator> rel_ops::operator<= rel_ops::operator>=

Pares y tuplas Original: Pairs and tuples The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.

pair

tuple (C++11)

piecewise_construct_t (C++11)

piecewise_construct (C++11)

Cambiar, hacia adelante y mover Original: Swap, forward and move The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.

swap

forward (C++11)

move (C++11)

move_if_noexcept (C++11)

declval (C++11)

 

Objetos Function

Envoltorios de función Original: Function wrappers The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
function (C++11)
mem_fn (C++11)
bad_function_call (C++11)
Enlazar Original: Bind The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
bind (C++11)
is_bind_expression (C++11)
is_placeholder (C++11)
_1, _2, _3, ... (C++11)
Envolturas de referencia Original: Reference wrappers The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
reference_wrapper (C++11)
ref cref (C++11) (C++11)
Envoltorios Operador Original: Operator wrappers The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
plus minus negate multiplies divides modulus logical_and logical_or logical_not	equal_to not_equal_to greater less greater_equal less_equal bit_and bit_or bit_xor
Negadores Original: Negators The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
unary_negate binary_negate	not1 not2
Desaprobado aglutinantes y adaptadores Original: Deprecated binders and adaptors The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
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>
extern /*unspecified*/ _1; extern /*unspecified*/ _2; . . extern /*unspecified*/ _N;

El espacio de nombres std::placeholders contiene los objetos de marcador de posición [_1, . . . _N] donde N es una aplicación definida número máximo .

Original:

The std::placeholders namespace contains the placeholder objects [_1, . . . _N] where N is an implementation defined maximum number.

The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.

Cuando se utiliza como un argumento en una expresión std::bind, los objetos de marcador de posición se almacenan en el objeto de la función generada, y cuando ese objeto se invoca la función con argumentos no consolidados, cada _N marcador de posición se sustituye por el argumento no unida enésima correspondiente .

Original:

When used as an argument in a std::bind expression, the placeholder objects are stored in the generated function object, and when that function object is invoked with unbound arguments, each placeholder _N is replaced by the corresponding Nth unbound argument.

The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.

Los tipos de los objetos de marcador de posición son DefaultConstructible y CopyConstructible, su copia por omisión / move constructores no producen excepciones, y para cualquier _N marcador de posición, la std::is_placeholder<decltype(_N)> tipo se define y se deriva de std::integral_constant<int, N> .

Original:

The types of the placeholder objects are DefaultConstructible and CopyConstructible, their default copy/move constructors do not throw exceptions, and for any placeholder _N, the type std::is_placeholder<decltype(_N)> is defined and is derived from std::integral_constant<int, N>.

The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.

Ejemplo

El siguiente código muestra la creación de objetos de función con un argumento marcador de posición .

Original:

The following code shows the creation of function objects with a placeholder argument.

The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.

#include <functional>
#include <string>
#include <iostream>
 
void goodbye(const std::string& s)
{
    std::cout << "Goodbye " << s << '\n';
}
 
class Object {
public:
    void hello(const std::string& s)
    {
        std::cout << "Hello " << s << '\n';
    }
};
 
int main(int argc, char* argv[])
{
    typedef std::function<void(const std::string&)> ExampleFunction;
    Object instance;
    std::string str("World");
    ExampleFunction f = std::bind(&Object::hello, &instance, 
                                  std::placeholders::_1);
 
    // equivalent to instance.hello(str)
    f(str);
    f = std::bind(&goodbye, std::placeholders::_1);
 
    // equivalent to goodbye(str)
    f(str);    
    return 0;
}

Output:

Hello World
Goodbye World

Ver también

bind (C++11)	se une uno o más argumentos a un objeto de función Original: binds one or more arguments to a function object The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (función de plantilla)
is_placeholder (C++11)	indica que un objeto es un marcador de posición estándar o se puede usar como una Original: indicates that an object is a standard placeholder or can be used as one The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (clase de plantilla)