std::mem_fn

 

C++

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initializer_list (C++11)

bitset

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

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pair

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piecewise_construct (C++11)

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swap

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declval (C++11)

 

Функция объектов

Функция обертки 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)
Привязка 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)
Ссылка обертки 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)
Оператор обертки 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
Negators 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
Устаревшие связующих и адаптеры 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 (устарело)
binary_function (устарело)
ptr_fun (устарело)
pointer_to_unary_function (устарело)
pointer_to_binary_function (устарело)
mem_fun (устарело)
mem_fun_t mem_fun1_t const_mem_fun_t const_mem_fun1_t (устарело) (устарело) (устарело) (устарело)
mem_fun_ref (устарело)
mem_fun_ref_t mem_fun1_ref_t const_mem_fun_ref_t const_mem_fun1_ref_t (устарело) (устарело) (устарело) (устарело)
binder1st binder2nd (устарело) (устарело)
bind1st bind2nd (устарело) (устарело)

 

Заголовочный файл <functional>
template< class R, class T > /*unspecified*/ mem_fn(R T::* pm);	(1)	(начиная с C++11)
template< class R, class T, class... Args > /*unspecified*/ mem_fn(R (T::* pm)(Args...)); template< class R, class T, class... Args > /*unspecified*/ mem_fn(R (T::* pm)(Args...) const); template< class R, class T, class... Args > /*unspecified*/ mem_fn(R (T::* pm)(Args...) volatile); template< class R, class T, class... Args > /*unspecified*/ mem_fn(R (T::* pm)(Args...) const volatile); template< class R, class T, class... Args > /*unspecified*/ mem_fn(R (T::* pm)(Args...) &); template< class R, class T, class... Args > /*unspecified*/ mem_fn(R (T::* pm)(Args...) const &); template< class R, class T, class... Args > /*unspecified*/ mem_fn(R (T::* pm)(Args...) volatile &); template< class R, class T, class... Args > /*unspecified*/ mem_fn(R (T::* pm)(Args...) const volatile &); template< class R, class T, class... Args > /*unspecified*/ mem_fn(R (T::* pm)(Args...) &&); template< class R, class T, class... Args > /*unspecified*/ mem_fn(R (T::* pm)(Args...) const &&); template< class R, class T, class... Args > /*unspecified*/ mem_fn(R (T::* pm)(Args...) volatile &&); template< class R, class T, class... Args > /*unspecified*/ mem_fn(R (T::* pm)(Args...) const volatile &&);	(2)	(C + +11, но дефект)

std::mem_fn функции шаблонов генерирует обертку объектов для указателей на члены, которые могут хранить, копировать, и ссылаться на указатель на член. Обе ссылки и указатели (в том числе смарт-указатели), чтобы объект может быть использован при вызове std::mem_fn.

Original:

Function template std::mem_fn generates wrapper objects for pointers to members, which can store, copy, and invoke a pointer to member. Both references and pointers (including smart pointers) to an object can be used when invoking a std::mem_fn.

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Перегрузок (2) представлены как дефект.

Original:

The overloads (2) are reported as defect.

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resolution, который недавно был признан "Ориентировочно Ready" предлагает удалить все перегрузок (2).

Original:

The resolution, which has recently been voted "Tentatively Ready" proposes to remove all the overloads (2).

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Это нарушит код, см. пример 3.

Original:

This will break some code, see Example 3.

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Параметры

pm

-

указатель на член, который будет обернут Original: pointer to member that will be wrapped The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.

Возвращаемое значение

std::mem_fn возвращает вызова оболочки неопределенного типа, который имеет следующие элементы:

Original:

std::mem_fn returns an call wrapper of unspecified type that has the following members:

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зЬй :: mem_fn

Original:

std::mem_fn

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Return type

Member types

типа Original: type The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.	definition
result_type	возвращаемого типа pm если pm является указателем на функцию-член, не определено для указателя на член объекта Original: the return type of pm if pm is a pointer to member function, not defined for pointer to member object The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
argument_type	T*, возможно, резюме квалифицированных, если pm является указателем на функцию-член не принимает аргументов Original: T*, possibly cv-qualified, if pm is a pointer to member function taking no arguments The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
first_argument_type	T* если pm является указателем на функцию-член принимает один аргумент Original: T* if pm is a pointer to member function taking one argument The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
second_argument_type	T1 если pm является указателем на функцию-член принимает один аргумент типа T1 Original: T1 if pm is a pointer to member function taking one argument of type T1 The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.

Member function

operator()	вызывает мишени на указанный объект, с дополнительными параметрами Original: invokes the target on a specified object, with optional parameters The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (public функция-член)

Исключения

Ни.

Original:

None.

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Пример 1

Используйте mem_fn хранить и выполнять функции члена и члена объекта

Original:

Use mem_fn to store and execute a member function and a member object:

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#include <functional>
#include <iostream>
 
struct Foo {
  void display_greeting() {
    std::cout << "Hello, world.\n";
  }
  void display_number(int i) {
    std::cout << "number: " << i << '\n';
  }
  int data = 7;
};
 
int main() {
  Foo f;
 
  auto greet = std::mem_fn(&Foo::display_greeting);
  greet(f);
 
  auto print_num = std::mem_fn(&Foo::display_number);
  print_num(f, 42);
 
  auto access_data = std::mem_fn(&Foo::data);
  std::cout << "data: " << access_data(f) << '\n';
}

Вывод:

Hello, world.
number: 42
data: 7

Пример 2

Передать функцию, чтобы std::transform создать комбинацию цифр:

Original:

Pass a member function to std::transform to create a sequence of numbers:

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#include <iostream>
#include <functional>
#include <iterator>
#include <memory>
#include <string>
#include <vector>
#include <algorithm>
 
int main()
{
    std::vector<std::string> words = {"This", "is", "a", "test"};
    std::vector<std::unique_ptr<std::string>> words2;
    words2.emplace_back(new std::string("another"));
    words2.emplace_back(new std::string("test"));
 
    std::vector<std::size_t> lengths;
    std::transform(words.begin(),
                   words.end(),
                   std::back_inserter(lengths),
                   std::mem_fn(&std::string::size)); // uses references to strings
    std::transform(words2.begin(),
                   words2.end(),
                   std::back_inserter(lengths),
                   std::mem_fn(&std::string::size)); // uses unique_ptr to strings
 
    std::cout << "The string lengths are ";
    for(auto n : lengths) std::cout << n << ' ';
    std::cout << '\n';
}

Вывод:

The string lengths are 4 2 1 4 7 4

Пример 3

#include <functional>
 
struct X {
  int x;
 
        int& easy()      {return x;}
        int& get()       {return x;}
  const int& get() const {return x;}
};
 
 
int main(void)
{
    auto a = std::mem_fn        (&X::easy); // no problem at all
//  auto b = std::mem_fn<int&  >(&X::get ); // no longer works with new specification
    auto c = std::mem_fn<int&()>(&X::get ); // works with both old and new specification
    auto d = [] (X& x) {return x.get();};   // another approach to overload resolution
}

См. также

function (C++11)	обертывания вызываемый объект любого типа с заданной подписью вызова функции Original: wraps callable object of any type with specified function call signature The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (шаблон класса)
bind (C++11)	связывает одну или несколько аргументов функции объекта 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. (шаблон функции)