Boost學習筆記3-Boost-Tuple

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---

title: Boost學習筆記3 - Boost::Tuple
mathjax: true
date: 2020-03-17 18:13:25
categories: [c++筆記,Boost學習筆記]
tags: [c++筆記,Boost學習筆記]
keywords: [c++筆記,Boost學習筆記]

---

Boost::Tuple

   boost::tuple是一個元組。在c++11被編入STL
   第六行無法通過編譯，這說明tuple的長度最長只能是10
   第9-12行定義了3個元組
   第13行演示瞭如何通過make_tuple構造元組
   第14行演示瞭如何通過get來訪問元組裏面的元素
   第16行演示了get的返回值是引用
   第19-20行演示了tuple的等號操作
   第23-27行演示了tuple中可以儲存引用
   第28行通過tie構造了一個全引用元組

#include <boost/tuple/tuple.hpp>
#include <boost/tuple/tuple_comparison.hpp>
#include <boost/tuple/tuple_io.hpp>
#include <bits/stdc++.h>

// boost::tuple<int, int, int, int, int, int, int, int, int, int, int>too_long;
int main() {
  // 基本操作
  boost::tuple<int, int, int, int, int, int, int, int, int, int> a(
      1, 2, 3, 4, 5, 6, 7, 8, 9, 10);
  boost::tuple<std::string, std::string> b("hello", "world");
  boost::tuple<std::string, std::string> c("hello", "world2");
  std::cout << boost::make_tuple(1, 2, 3, 4) << std::endl;
  std::cout << "a.get<0>() is " << a.get<0>() << std::endl;
  std::cout << "a is " << a << std::endl;
  a.get<0>() = -1;
  std::cout << "a is " << a << std::endl;
  std::cout << "b is " << b << std::endl;
  std::cout << "b==c is " << (b == c) << std::endl;
  std::cout << "b==b is " << (b == b) << std::endl;

  // 進階操作
  int x = 1, y = 2;
  boost::tuple<int&, int> reference(boost::ref(x), y);
  // boost::tuple<int&, int> reference(x, y); 也可以
  x = 5;
  std::cout << "reference is " << reference << std::endl;
  auto reference2 = boost::tie(x, y);
  x = 10, y = 11;
  std::cout << "reference2 is " << reference2 << std::endl;
}

輸出

(1 2 3 4)
a.get<0>() is 1
a is (1 2 3 4 5 6 7 8 9 10)
a is (-1 2 3 4 5 6 7 8 9 10)
b is (hello world)
b==c is 0
b==b is 1
reference is (5 2)
reference2 is (10 11)