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std::tuple_size<std::pair>

提供: cppreference.com
< cpp‎ | utility‎ | pair

 
 
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
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rel_ops::operator!=
rel_ops::operator>
rel_ops::operator<=
rel_ops::operator>=
ペアとタプル
Original:
Pairs and tuples
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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
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swap
forward(C++11)
move(C++11)
move_if_noexcept(C++11)
declval(C++11)
 
std::pair
メンバ関数
Original:
Member functions
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pair::pair
pair::operator=
pair::swap
非メンバ関数
Original:
Non-member functions
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make_pair
operator=
operator!=
operator<
operator<=
operator>
operator>=
std::swap
get(C++11)
ヘルパークラス
Original:
Helper classes
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tuple_size(C++11)
tuple_element(C++11)
 
Defined in header <utility>
template< class T1, class T2 >
struct tuple_size<std::pair<T1, T2>>;
(C++11およびそれ以降)

The partial specialization of std::tuple_size for pairs provides a compile-time way to obtain the number of elements in a pair, which is always 2, using tuple-like syntax.

Members

value
[静的]
integral constant with value 2
(パブリック静的メンバ定数)

[編集]

#include <iostream>
#include <utility>
#include <tuple>
 
template<class T>
void test(T t)
{
    int a[std::tuple_size<T>::value]; // can be used at compile time
    std::cout << std::tuple_size<T>::value << '\n'; // or at run time
}
 
int main()
{
    test(std::make_tuple(1, 2, 3.14));
    test(std::make_pair(1, 3.14));
}

Output:

3
2

[編集] も参照してください

コンパイル時にtupleのサイズを取得します
Original:
obtains the size of tuple at compile time
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(クラステンプレートの特殊化の2つの値を比較します) [edit]
arrayのサイズを取得します
Original:
obtains the size of an array
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(クラステンプレートの特殊化の2つの値を比較します) [edit]
pairの要素の型を取得します
Original:
obtains the type of the elements of pair
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(クラステンプレートの特殊化の2つの値を比較します) [edit]