名前空間
変種
操作

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

提供: cppreference.com
< cpp‎ | utility‎ | functional

 
 
ユーティリティライブラリ
支援を入力します (basic types, RTTI, type traits)
動的なメモリ管理
エラー処理
プログラムユーティリティ
可変個引数関数
日付と時刻
関数オブジェクト
initializer_list(C++11)
bitset
hash(C++11)
関係演算子
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>=
ペアとタプル
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)
フォワード、スワップ、および移動
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)
 
関数オブジェクト
関数ラッパー
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)
バインド
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)
リファレンス·ラッパー
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)
オペレーターのラッパー
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.
否定子
Original:
Negators
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
バインダーおよびアダプタは非推奨になりました
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(廃止予定)
binary_function(廃止予定)
ptr_fun(廃止予定)
pointer_to_unary_function(廃止予定)
pointer_to_binary_function(廃止予定)
mem_fun(廃止予定)
mem_fun_t
mem_fun1_t
const_mem_fun_t
const_mem_fun1_t
(廃止予定)
(廃止予定)
(廃止予定)
(廃止予定)
mem_fun_ref(廃止予定)
mem_fun_ref_t
mem_fun1_ref_t
const_mem_fun_ref_t
const_mem_fun1_ref_t
(廃止予定)
(廃止予定)
(廃止予定)
(廃止予定)
binder1st
binder2nd
(廃止予定)
(廃止予定)
bind1st
bind2nd
(廃止予定)
(廃止予定)
 
Defined in header <functional>
extern /*unspecified*/ _1;

extern /*unspecified*/ _2;
.
.

extern /*unspecified*/ _N;
std::placeholders名前空間には、プレースホルダオブジェクト[_1, . . . _N]Nが最大数を定義して実装したものです含まれています.
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.
std::bind式で引数として使用される場合、プレースホルダー·オブジェクトが生成された関数オブジェクトに格納され、その関数オブジェクトがバインドされていない引数を使って呼び出されたときに、各プレースホルダ_Nは、対応するN番目のバインドされていない引数に置き換えられます.
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.
プレースホルダオブジェクトのタイプは、DefaultConstructibleCopyConstructible、それらのデフォルトのコピー/ムーブコンストラクタは例外をスローしない、任意のプレースホルダ_Nでは、タイプstd::is_placeholder<decltype(_N)>が定義されているとstd::integral_constant<int, N>から導出され.
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.

[編集]

次のコードは、プレースホルダの引数を持つ関数オブジェクトの作成方法を示しています.
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

[編集] も参照してください

(C++11)
関数オブジェクトに1つ以上の引数をバインドします
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.

(関数テンプレート) [edit]
オブジェクトは、標準のプレースホルダーであることを示し、または1つとして使用することができます
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.

(クラステンプレート) [edit]