tuple元组（C++11及以后，如C++14）

类tuple与array最本质的区别当数tuple元组元素类型可以不一样，而统一数组array的元素类型必须一样。

本文主要举例：

tuple_size

Example

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// tuple example #include <iostream> // std::cout #include <tuple> // std::tuple, std::get, std::tie, std::ignore int main () { std::tuple<int,char> foo (10,'x'); auto bar = std::make_tuple ("test", 3.1, 14, 'y'); std::get<2>(bar) = 100; // access element int myint; char mychar; std::tie (myint, mychar) = foo; // unpack elements std::tie (std::ignore, std::ignore, myint, mychar) = bar; // unpack (with ignore) mychar = std::get<3>(bar); std::get<0>(foo) = std::get<2>(bar); std::get<1>(foo) = mychar; std::cout << "foo contains: "; std::cout << std::get<0>(foo) << ' '; std::cout << std::get<1>(foo) << '\n'; return 0; }

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Output:

foo contains: 100 y

tie----（unpack）

Example

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// packing/unpacking tuples #include <iostream> // std::cout #include <tuple> // std::tuple, std::make_tuple, std::tie int main () { int myint; char mychar; std::tuple<int,float,char> mytuple; mytuple = std::make_tuple (10, 2.6, 'a'); // packing values into tuple std::tie (myint, std::ignore, mychar) = mytuple; // unpacking tuple into variables std::cout << "myint contains: " << myint << '\n'; std::cout << "mychar contains: " << mychar << '\n'; return 0; }

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Output:

myint contains: 10
mychar contains: a

std:tuple_element

Member types

member type	definition
type	The Ith type in the tuple object

Example

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// tuple_element #include <iostream> // std::cout #include <tuple> // std::tuple, std::make_tuple, std::tuple_element, std::get int main () { auto mytuple = std::make_tuple (10,'a'); std::tuple_element<0,decltype(mytuple)>::type first = std::get<0>(mytuple); std::tuple_element<1,decltype(mytuple)>::type second = std::get<1>(mytuple); std::cout << "mytuple contains: " << first << " and " << second << '\n'; return 0; }

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Output:

mytuple contains: 10 and a

tuple_size

Member constants

member constant	definition
value	The number of elements in the tuple or tuple-like object. This is a constexpr value of the unsigned integral type size_t.

Example

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// tuple_size #include <iostream> // std::cout #include <tuple> // std::tuple, std::tuple_size int main () { std::tuple<int,char,double> mytuple (10,'a',3.14); std::cout << "mytuple has "; std::cout << std::tuple_size<decltype(mytuple)>::value; std::cout << " elements." << '\n'; return 0; }

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Output:

mytuple has 3 elements

forward_as_tuple

Parameters

args

List of elements to be forwarded as a tuple object of references.

Return Value

A tuple object with rvalue references to args suitable to be forwarded as argument to a function.

Example

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// forward_as_tuple example #include <iostream> // std::cout #include <tuple> // std::tuple, std::get, std::forward_as_tuple #include <string> // std::string void print_pack (std::tuple<std::string&&,int&&> pack) { std::cout << std::get<0>(pack) << ", " << std::get<1>(pack) << '\n'; } int main() { std::string str ("John"); print_pack (std::forward_as_tuple(str+" Smith",25)); print_pack (std::forward_as_tuple(str+" Daniels",22)); return 0; }

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Output:

John Smith, 25
John Daniels, 22

tuple_cat

Parameters

tpls

Comma-separated list of tuple objects. These may be of different types.

Return Value

A tuple object of the appropriate type to hold args.

The type of the returned object (tuple<CTypes...>) is the tuple type that contains the ordered sequence of all the extended types inTuples.

Example

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// tuple_cat example #include <iostream> // std::cout #include <utility> // std::pair #include <string> // std::string #include <tuple> // std::tuple, std::tuple_cat, std::get int main () { std::tuple<float,std::string> mytuple (3.14,"pi"); std::pair<int,char> mypair (10,'a'); auto myauto = std::tuple_cat ( mytuple, std::tuple<int,char>(mypair) ); std::cout << "myauto contains: " << '\n'; std::cout << std::get<0>(myauto) << '\n'; std::cout << std::get<1>(myauto) << '\n'; std::cout << std::get<2>(myauto) << '\n'; std::cout << std::get<3>(myauto) << '\n'; return 0; }

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Output:

myauto contains:
3.14
pi
10
a

ignore tie

Parameters

args

List of objects (lvalues) to be tied as elements of a tuple.

Return Value

A tuple with lvalue references to args.

Example

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// packing/unpacking tuples #include <iostream> // std::cout #include <tuple> // std::tuple, std::make_tuple, std::tie int main () { int myint; char mychar; std::tuple<int,float,char> mytuple; mytuple = std::make_tuple (10, 2.6, 'a'); // packing values into tuple std::tie (myint, std::ignore, mychar) = mytuple; // unpacking tuple into variables std::cout << "myint contains: " << myint << '\n'; std::cout << "mychar contains: " << mychar << '\n'; return 0; }

Edit & Run

Output:

myint contains: 10
mychar contains: a