C++11 tuple(元组)
tuple是C++11中引入的新类型，中文翻译就是元组。元组是一个能够容纳元素集合的对象。 每个元素可以具有不同的类型。类模板std :: tuple是固定大小的异构值集合。具体可以参考tuple-cppreference.com和tuple-cplusplus.com中的描述，并且提供了一些示例程序。
在使用tuple之前需要导入对应的头文件：#include
tuple的原型声明如下：
template< class... Types >
class tuple; (C++11)
其中，tuple-cplusplus.com中提供的示例程序如下：
// 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;
}
OutPut:
foo contains: 100 y
C++中使用tuple和pair可以返回多个不同类型的多个值。示例程序如下：
#include<bits/stdc++.h>
using namespace std;
// A Method that returns multiple values using
// tuple in C++.
tuple<int, int, char> foo(int n1, int n2)
{
// Packing values to return a tuple
return make_tuple(n2, n1, 'a');
}
// A Method returns a pair of values using pair
std::pair<int, int> foo1(int num1, int num2)
{
// Packing two values to return a pair
return std::make_pair(num2, num1);
}
int main()
{
int a,b;
char cc;
// Unpack the elements returned by foo
tie(a, b, cc) = foo(5, 10);
// Storing returned values in a pair
pair<int, int> p = foo1(5,2);
cout << "Values returned by tuple: ";
cout << a << " " << b << " " << cc << endl;
cout << "Values returned by Pair: ";
cout << p.first << " " << p.second;
return 0;
}
Output
Values returned by tuple: 10 5 a
Values returned by Pair: 2 5
C++中的tuple
什么是tuple元组?
tuple是可以容纳许多元素的独享。元素可以是不同的数据类型。元组中的元素被初始化为参数，以便可以访问它们。
元组上的操作
- 1.get() : - get()用于访问元组值并对其进行修改，它接受索引和元组名称作为访问特定元组元素的参数。
- 2.make_tuple() : -make_tuple()用于为元组分配值。传递的值应与在tuple中声明的值一致。
// C++ code to demonstrate tuple, get() and make_pair()
#include<iostream>
#include<tuple> // for tuple
using namespace std;
int main()
{
// Declaring tuple
tuple <char, int, float> geek;
// Assigning values to tuple using make_tuple()
geek = make_tuple('a', 10, 15.5);
// Printing initial tuple values using get()
cout << "The initial values of tuple are : ";
cout << get<0>(geek) << " " << get<1>(geek);
cout << " " << get<2>(geek) << endl;
// Use of get() to change values of tuple
get<0>(geek) = 'b';
get<2>(geek) = 20.5;
// Printing modified tuple values
cout << "The modified values of tuple are : ";
cout << get<0>(geek) << " " << get<1>(geek);
cout << " " << get<2>(geek) << endl;
return 0;
}
输出：
The initial values of tuple are : a 10 15.5
The modified values of tuple are : b 10 20.5
在以上代码中，get()修改tuple的第1个和第3个值。
- 3.tuple_size :-返回tuple中存在的元素数。
//C++ code to demonstrate tuple_size
#include<iostream>
#include<tuple> // for tuple_size and tuple
using namespace std;
int main()
{
// Initializing tuple
tuple <char,int,float> geek(20,'g',17.5);
// Use of size to find tuple_size of tuple
cout << "The size of tuple is : ";
cout << tuple_size<decltype(geek)>::value << endl;
return 0;
}
输出：
The size of tuple is : 3
- 4.swap() :-swap()交换两个不同的元组中的元素。
//C++ code to demonstrate swap()
#include<iostream>
#include<tuple> // for swap() and tuple
using namespace std;
int main()
{
// Initializing 1st tuple
tuple <int,char,float> tup1(20,'g',17.5);
// Initializing 2nd tuple
tuple <int,char,float> tup2(10,'f',15.5);
// Printing 1st and 2nd tuple before swapping
cout << "The first tuple elements before swapping are : ";
cout << get<0>(tup1) << " " << get<1>(tup1) << " "
<< get<2>(tup1) << endl;
cout << "The second tuple elements before swapping are : ";
cout << get<0>(tup2) << " " << get<1>(tup2) << " "
<< get<2>(tup2) << endl;
// Swapping tup1 values with tup2
tup1.swap(tup2);
// Printing 1st and 2nd tuple after swapping
cout << "The first tuple elements after swapping are : ";
cout << get<0>(tup1) << " " << get<1>(tup1) << " "
<< get<2>(tup1) << endl;
cout << "The second tuple elements after swapping are : ";
cout << get<0>(tup2) << " " << get<1>(tup2) << " "
<< get<2>(tup2) << endl;
return 0;
}
输出：
The first tuple elements before swapping are : 20 g 17.5
The second tuple elements before swapping are : 10 f 15.5
The first tuple elements after swapping are : 10 f 15.5
The second tuple elements after swapping are : 20 g 17.5
-
- tie() :- tie()的工作是将元组值解包到单独的变量中。 tie()有两种变体，有和没有“ ignore”，“ ignore”将忽略特定的元组元素并阻止其解压缩。
// C++ code to demonstrate working of tie()
#include<iostream>
#include<tuple> // for tie() and tuple
using namespace std;
int main()
{
// Initializing variables for unpacking
int i_val;
char ch_val;
float f_val;
// Initializing tuple
tuple <int,char,float> tup1(20,'g',17.5);
// Use of tie() without ignore
tie(i_val,ch_val,f_val) = tup1;
// Displaying unpacked tuple elements
// without ignore
cout << "The unpacked tuple values (without ignore) are : ";
cout << i_val << " " << ch_val << " " << f_val;
cout << endl;
// Use of tie() with ignore
// ignores char value
tie(i_val,ignore,f_val) = tup1;
// Displaying unpacked tuple elements
// with ignore
cout << "The unpacked tuple values (with ignore) are : ";
cout << i_val << " " << f_val;
cout << endl;
return 0;
}
输出：
The unpacked tuple values (without ignore) are : 20 g 17.5
The unpacked tuple values (with ignore) are : 20 17.5
-
- tuple_cat() :- 此函数连接两个元组并返回一个新的元组。
// C++ code to demonstrate working of tuple_cat()
#include<iostream>
#include<tuple> // for tuple_cat() and tuple
using namespace std;
int main()
{
// Initializing 1st tuple
tuple <int,char,float> tup1(20,'g',17.5);
// Initializing 2nd tuple
tuple <int,char,float> tup2(30,'f',10.5);
// Concatenating 2 tuples to return a new tuple
auto tup3 = tuple_cat(tup1,tup2);
// Displaying new tuple elements
cout << "The new tuple elements in order are : ";
cout << get<0>(tup3) << " " << get<1>(tup3) << " ";
cout << get<2>(tup3) << " " << get<3>(tup3) << " ";
cout << get<4>(tup3) << " " << get<5>(tup3) << endl;
return 0;
}
输出：
The new tuple elements in order are : 20 g 17.5 30 f 10.5