C++11 tuple的用法浅析

水深无声 2023-07-07 08:58 2阅读 0赞

tuple 元组定义了一个有固定数目元素的容器，其中的每个元素类型都可以不相同，这与其他容器有着本质的区别，是对pair的泛化，可以用于函数返回多个返回值。

以下代码是关于tuple使用的一些示例，一部分来源于网上，经过整理后发出来

#include "stdafx.h"
    #include <iostream>
    #include <tuple>
    #include <functional>
    #include <utility>//std::pair
    #include <string>
    
    /**
     * @brief 通过make_tuple()创建元组,通过get<>()来访问元组的元素。
     */
    void make_tuple_demo()
    {
    	//创建元组
    	auto itr = std::make_tuple(10, "Test", 3.14);
    	std::cout << "The value of t1 is "
    		<< "(" << std::get<0>(itr) << ", "
    		<< std::get<1>(itr) << ", "
    		<< std::get<2>(itr) << ")\n";
    
    	int n = 1;
    	auto it = std::make_tuple(std::ref(n), n);//ref表示引用
    	n = 7;
    
    	std::cout << "The value of t2 is "
    		<< "(" << std::get<0>(it) << ", "
    		<< std::get<1>(it) << ")\n";
    
    	getchar();
    }
    
    /**
     * @brief 通过tie()函数对tuple进行"解包"操作
     */
    void tie_demo()
    {
    	//
    	int myint;
    	char mychar;
    	float myfloat;
    
    	std::tuple<int, float, char> mytuple;
    	mytuple = std::make_tuple(10, 2.6, 'a'); // packing values into tuple
    
    	//可以使用std::ignore,从而不用关联tuple中的第二个元素.
    	//std::tie (myint, std::ignore, mychar) = mytuple; 
    
    	// tie()函数可以将变量连接到一个给定的tuple上,生成一个元素类型全是引用的tuple
    	std::tie(myint, myfloat, mychar) = mytuple;
    
    	std::cout << "myint contains: " << myint << std::endl;
    	std::cout << "mychar contains: " << mychar << std::endl;
    	std::cout << "myfloat contains: " << myfloat << std::endl;
    	std::get<0>(mytuple) = 100;//修改tuple的值
    
    	std::cout << "After assignment myint contains: " << std::get<0>(mytuple) << std::endl;
    
    	getchar();
    }
    
    /**
     * @brief tuple_cat()函数,可将多个tuple连接起来形成一个tuple
     */
    void tuple_cat_demo()
    {
    	//注:在VC11中只能连接两个tuple并不是真正的多个tuple
    	std::tuple<float, std::string> tuple1st(3.14, "pi");
    	std::pair<int, char> pair2nd(10, 'a');
    
    	auto myauto = std::tuple_cat(tuple1st, pair2nd);
    	std::cout << "myauto contains: " << std::endl;
    	std::cout << std::get<0>(myauto) << std::endl;
    	std::cout << std::get<1>(myauto) << std::endl;
    	std::cout << std::get<2>(myauto) << std::endl;
    	std::cout << std::get<3>(myauto) << std::endl;
    
    	getchar();
    }
    
    /**
     * @brief 获取元素数量&获取元素类型
     */
    void tuple_size_test()
    {
    	//可以直接初始化
    	std::tuple<int, double, std::string> t(64, 128.0, "Caroline");
    
    	//可以通过"std::tuple_size<decltype(t)>::value"获取元素数量	
    	size_t num = std::tuple_size<decltype(t)>::value;
    	std::cout << "num = " << num << std::endl;
    
    	//可以通过"std::tuple_element<0, decltype(t)>::type"获取元素类型
    	std::tuple_element<1, decltype(t)>::type cnt = std::get<1>(t);
    	std::cout << "cnt = " << cnt << std::endl;
    }
    
    
    
    int main()
    {
    	make_tuple_demo();
    	/*
    		The value of t1 is (10, Test, 3.14)
    		The value of t2 is (7, 1)
    	*/
    
    	tie_demo();
    	/*
    		myint contains: 10
    		mychar contains: a
    		myfloat contains: 2.6
    		After assignment myint contains: 100
    	*/
    
    	tuple_cat_demo();
    	/*
    		myauto contains:
    		3.14
    		pi
    		10
    		a
    	*/
    
    	tuple_size_test();
    	/*
    		num = 3
    		cnt = 128
    	*/
    
        return 0;
    }