std::tuple是C++ 11中引入的一个非常有用的结构，以前我们要返回一个包含不同数据类型的返回值，一般都需要自定义一个结构体或者通过函数的参数来返回，现在std::tuple就可以帮我们搞定。
1.引用头文件
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#include <tuple> |
2. Tuple初始化
std::tuple的初始化可以通过构造函数实现。
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// Creating and Initializing a tuplestd::tuple<int, double, std::string> result1 { 22, 19.28, "text" }; |
这种初始化方式要定义各个元素的数据类型，比较繁琐，C++11也提供了另外一种方式std::make_tuple。
3. std::make_tuple
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// Creating a tuple using std::make_tupleauto result2 = std::make_tuple( 7, 9.8, "text" ); |
这种初始化方式避免需要逐个指定元素类型的问题，自动化实现各个元素类型的推导。
完整例子一：
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#include <iostream>#include <tuple>#include <string>int main(){ // Creating and Initializing a tuple std::tuple<int, double, std::string> result1 { 22, 19.28, "text" }; // Compile error, as no way to deduce the types of elements in tuple //auto result { 22, 19.28, "text" }; // Compile error // Creating a tuple using std::make_tuple auto result2 = std::make_tuple( 7, 9.8, "text" ); // std::make_tuple automatically deduced the type and created tuple // Print values std::cout << "int value = " << std::get < 0 > (result2) << std::endl; std::cout << "double value = " << std::get < 1 > (result2) << std::endl; std::cout << "string value = " << std::get < 2 > (result2) << std::endl; return 0;} |
输出：
<strong>int</strong> value = 7
<strong>double</strong> value = 9.8
string value = text
完整例子二：
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#include <iostream>#include <tuple>#include <functional> std::tuple<int, int> f() // this function returns multiple values{ int x = 5; return std::make_tuple(x, 7); // return {x,7}; in C++17} int main(){ // heterogeneous tuple construction int n = 1; auto t = std::make_tuple(10, "Test", 3.14, std::ref(n), n); n = 7; std::cout << "The value of t is " << "(" << std::get<0>(t) << ", " << std::get<1>(t) << ", " << std::get<2>(t) << ", " << std::get<3>(t) << ", " << std::get<4>(t) << ")\n"; // function returning multiple values int a, b; std::tie(a, b) = f(); std::cout << a << " " << b << "\n";} |
输出：
The value of t is (10, Test, 3.14, 7, 1)
5 7
参考材料
https://thispointer.com/c11-make_tuple-tutorial-example/
https://en.cppreference.com/w/cpp/utility/tuple/make_tuple
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