C++ std::pair, std::tuple

std::pair 定义于<utility>

template <class T1, class T2> struct pair;

Pair of values

This class couples together a pair of values, which may be of different types (T1 and T2). The individual values can be accessed through its public members first and second.

std::tuple 定义于<tuple>

Tuple library

Tuples are objects that pack elements of -possibly- different types together in a single object, just like pairobjects do for pairs of elements, but generalized for any number of elements.Conceptually, they are similar to plain old data structures (C-like structs) but instead of having named data members, its elements are accessed by their order in the tuple.The selection of particular elements within a tuple is done at the template-instantiation level, and thus, it must be specified at compile-time, with helper functions such as get and tie.The tuple class is closely related to the pair class (defined in header <utility>): Tuples can be constructed from pairs, and pairs can be treated as tuples for certain purposes.array containers also have certain tuple-like functionalities.

#include <iostream>#include <tuple>#include <string>#include <utility>#include <stdexcept>std::tuple<double, char, std::string> get_student(int id) {  if (id == 0)    return std::make_tuple(98.5, 'A', "qsa");  if (id == 1)    return std::make_tuple(77.0, 'B', "bb");  throw std::invalid_argument("error !");}int main() {  auto student = get_student(0);  std::cout << "score " << std::get<0>(student)    << " level " << std::get<1>(student)    << " name " << std::get<2>(student) << std::endl;  double score;  char level;  std::string name;  std::tie(score, level, name) = get_student(1);  std::cout << "score " << score << " level " << level << " name " << name << std::endl;  std::pair<int, char> mypair(100, 'A');  auto coll = std::tuple_cat(student, mypair);  std::cout << std::get<0>(coll) << std::endl;  std::cout << std::get<1>(coll) << std::endl;  std::cout << std::get<2>(coll) << std::endl;  std::cout << std::get<3>(coll) << std::endl;  std::cout << std::get<4>(coll) << std::endl;}