std::forward_as_tuple

 

C++

語言

概念

實用工具庫

字元串庫

集裝箱庫

演算法庫

迭代器庫

Numerics庫

輸入/輸出庫

本地化庫

正則表達式庫 （C++11）

原子操作庫 （C++11）

線程的支持庫 （C++11）

 

實用工具庫

類型的支持 (basic types, RTTI, type traits)

動態內存管理

錯誤處理

程序實用工具

可變參數函數

日期和時間

函數對象

initializer_list （C++11）

bitset

hash （C++11）

關係運算符 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>=

雙和元組 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）

掉期，遠期和移動 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）

 

std::tuple

成員函數 Original: Member functions The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.

tuple::tuple

tuple::operator=

tuple::swap

非成員函數 Original: Non-member functions The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.

make_tuple

tie

forward_as_tuple

None

operator= operator!= operator< operator<= operator> operator>=

std::swap

get

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

tuple_size

tuple_element

uses_allocator

ignore

 

Defined in header <tuple>
template< class... Types > tuple<Types...> forward_as_tuple( Types&&... args );		（C++11 起）

構造一個元組中的參數args適合作為函數的參數進行轉發。該元組的右值引用的數據成員時，右值作為參數，否則有左值引用的數據成員。如果右值使用此功能前必須消耗的下一個序列點，結果.

Original:

Constructs a tuple of references to the arguments in args suitable for forwarding as an argument to a function. The tuple has rvalue reference data members when rvalues are used as arguments, and otherwise has lvalue reference data members. If rvalues are used, the result of this function must be consumed before the next sequence point.

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

參數

args

-

零個或多個參數來構造的元組 Original: zero or more arguments to construct the tuple from The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.

返回值

一個std::tuple創建的對象，如果std::tuple<Types&&...>(std::forward<Types>(args)...)

Original:

A std::tuple object created as if by std::tuple<Types&&...>(std::forward<Types>(args)...)

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

例外

noexcept specification:  

noexcept

  （C++11 起）

為例

#include <iostream>
#include <map>
#include <tuple>
#include <string>
 
int main()
{
    std::map<int, std::string> m;
 
    // same as m.emplace(10, 20, 'a');
    m.emplace(std::forward_as_tuple(10, std::string(20, 'a')));
    std::cout << "m[10] = " << m[10] << '\n';
 
    // The following is an error: it produces a
    // std::tuple<int&&, std::string&&> holding two dangling references.
    //
    // auto t = std::forward_as_tuple(10, std::string(20, 'a'));
    // m.emplace(t);
}

Output:

m[10] = aaaaaaaaaaaaaaaaaaaa

make_tuple	創建一個tuple對象的參數類型定義的類型 Original: creates a tuple object of the type defined by the argument types The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. （函數模板）
tie	創建一個tuple的左值引用或解壓縮到單個對象的元組 Original: creates a tuple of lvalue references or unpacks a tuple into individual objects The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. （函數模板）
tuple_cat	創建一個tuple通過連接任意數量的元組 Original: creates a tuple by concatenating any number of tuples The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. （函數模板）