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蓝桥ROS机器人之现代C++学习笔记2.2变量及其初始化_ros中c_cpp中的include变量会变

作者：AllinToyou | 2024-02-18 04:43:54

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ros中c_cpp中的include变量会变

if/switch 变量声明强化

  1. #include <iostream>
  2. #include <vector>
  3. #include <algorithm>
  4.  
  5. int main() {
  6.     std::vector<int> vec = {1, 2, 3, 4};
  7.  
  8.     // after c++17, can be simplefied by using `auto`
  9.     const std::vector<int>::iterator itr = std::find(vec.begin(), vec.end(), 2);
  10.     if (itr != vec.end()) {
  11.         *itr = 3;
  12.     }
  13.  
  14.     const std::vector<int>::iterator itr1 = std::find(vec.begin(), vec.end(), 3);
  15.     if (itr1 != vec.end()) {
  16.         *itr1 = 4;
  17.     }
  18.  
  19.     // should output: 1, 4, 3, 4. can be simplefied using `auto`
  20.     for (std::vector<int>::iterator element = vec.begin(); element != vec.end(); ++element)
  21.         std::cout << *element << std::endl;
  22. }

g++ -std=c++17 2.03.if.switch.cpp -o ifswitch

初始化列表 

  1. include <iostream>
  2. #include <initializer_list>
  3. #include <vector>
  4.  
  5. class Foo {
  6. public:
  7.     int value_a;
  8.     int value_b;
  9.     Foo(int a, int b) : value_a(a), value_b(b) {}
  10. };
  11.  
  12. class MagicFoo {
  13. public:
  14.     std::vector<int> vec;
  15.     MagicFoo(std::initializer_list<int> list) {
  16.         for (std::initializer_list<int>::iterator it = list.begin(); it != list.end(); ++it) {
  17.             vec.push_back(*it);
  18.         }
  19.     }
  20.     void foo(std::initializer_list<int> list) {
  21.         for (std::initializer_list<int>::iterator it = list.begin(); it != list.end(); ++it) {
  22.             vec.push_back(*it);
  23.         }
  24.     }
  25. };
  26.  
  27. int main() {
  28.     // before C++11
  29.     int arr[3] = {1, 2, 3};
  30.     Foo foo(1, 2);
  31.     std::vector<int> vec = {1, 2, 3, 4, 5};
  32.  
  33.     // after C++11
  34.     MagicFoo magicFoo = {1, 2, 3, 4, 5};
  35.     magicFoo.foo({6,7,8,9});
  36.     Foo foo2 {3, 4};
  37.  
  38.     std::cout << "arr[0]: " << arr[0] << std::endl;
  39.     std::cout << "foo:" << foo.value_a << ", " << foo.value_b << std::endl;
  40.     std::cout << "vec: ";
  41.     for (std::vector<int>::iterator it = vec.begin(); it != vec.end(); ++it) {
  42.         std::cout << *it << std::endl;
  43.     }
  44.     std::cout << "magicFoo: ";
  45.     for (std::vector<int>::iterator it = magicFoo.vec.begin(); it != magicFoo.vec.end(); ++it) {
  46.         std::cout << *it << std::endl;
  47.     }
  48.     std::cout << "foo2: " << foo2.value_a << ", " << foo2.value_b << std::endl;
  49.  
  50.     return 0;
  51. }

g++ -std=c++17 2.04.initializer.list.cpp -o initlist 

结构化绑定

编译原有程序报错：

查阅 github.com/changkun/modern-cpp-tutorial/issues/166

并未得到合理解决。

提供资料如下：

  1. en.cppreference.com/w/cpp/utility/tuple
  2. riptutorial.com/cplusplus/example/1601/using-std--tuple

g++ 5 不支持

 

g++ 11 支持

 

 clang 5 也支持

程序没有问题，是编译器版本有点旧。

  1.  
  2. #include <iostream>
  3. #include <tuple>
  4. #include <string>
  5.  
  6. std::tuple<int, double, std::string> f() {
  7.     return std::make_tuple(1, 2.3, "456");
  8. }
  9.  
  10. int main() {
  11.     int x=0; 
  12.     double y=0.1;
  13.     std::string z="123";
  14.     std::cout << x << ", " << y << ", " << z << std::endl;
  15.     std:tie(x, y, z) = f();
  16.     std::cout << x << ", " << y << ", " << z << std::endl;
  17.     return 0;
  18. }

 

  1. shiyanlou:~/ $ ls                                                    [14:33:08]
  2. anaconda3  Code  Desktop
  3. shiyanlou:~/ $ history                                               [14:33:20]
  4.     1  git clone https://github.com/changkun/modern-cpp-tutorial.git
  5.     2  g++ -std=c++17 2.03.if.switch.cpp -o ifswitch
  6.     3  ./ifswitch
  7.     4  g++ -std=c++17 2.04.initializer.list.cpp -o initlist
  8.     5  ./initlist
  9.     6  g++ -std=c++17 2.05.structured.binding.cpp -o strubind
  10.     7  g++ -std=c++17 2.05.structured.binding.cpp -g -Wall -Wno-unused-variable -pthread -o strubind
  11.     8  g++ -std=c++17 2.05.structured.binding.cpp -o strubind
  12.     9  g++ -std=c++17 2.05.structured.binding.cpp -g -Wall -Wno-unused-variable -pthread -o strubind
  13.    10  g++ -std=c++17 2.05.structured.binding.cpp -o strubind
  14.    11  ./strubind
  15.    12  g++ -std=c++17 2.05.structured.binding.cpp -o strubind
  16.    13  ./strubind
  17.    14  gcc -v
  18.    15  g++ -v
  19.    16  ls
  20. shiyanlou:~/ $                                                       [14:33:24]
  21.  
  22.  
  1. shiyanlou:2/ (master) $ g++ -std=c++17 2.03.if.switch.cpp -o ifswitch 
  2. 2.03.if.switch.cpp: In function \u2018int main()\u2019:
  3. 2.03.if.switch.cpp:23:84: error: expected \u2018)\u2019 before \u2018;\u2019 token
  4.  f (const std::vector<int>::iterator itr = std::find(vec.begin(), vec.end(), 3);
  5.                                                                                ^
  6. 2.03.if.switch.cpp:23:84: error: could not convert \u2018itr\u2019 from \u2018const iterator {aka const __gnu_cxx::__normal_iterator<int*, std::vector<int> >}\u2019 to \u2018bool\u2019
  7. 2.03.if.switch.cpp:24:25: error: expected \u2018;\u2019 before \u2018)\u2019 token
  8.          itr != vec.end()) {
  9.                          ^
  10. shiyanlou:2/ (master) $ g++ -std=c++17 2.03.if.switch.cpp -o ifswitch
  11. 2.03.if.switch.cpp: In function \u2018int main()\u2019:
  12. 2.03.if.switch.cpp:23:38: error: redeclaration of \u2018const iterator itr\u2019
  13.      const std::vector<int>::iterator itr = std::find(vec.begin(), vec.end(), 3)
  14.                                       ^
  15. 2.03.if.switch.cpp:18:38: note: \u2018const iterator itr\u2019 previously declared here
  16.      const std::vector<int>::iterator itr = std::find(vec.begin(), vec.end(), 2)
  17.                                       ^
  18. shiyanlou:2/ (master*) $ g++ -std=c++17 2.03.if.switch.cpp -o ifswitch
  19. shiyanlou:2/ (master*) $ ./ifswitch                                  [13:42:51]
  20. 1
  21. 4
  22. 3
  23. 4
  24. shiyanlou:2/ (master*) $                                             [13:43:02]
  25. shiyanlou:2/ (master*) $ g++ -std=c++17 2.04.initializer.list.cpp -o initlist
  26. shiyanlou:2/ (master*) $ ./initlist                                  [13:46:31]
  27. arr[0]: 1
  28. foo:1, 2
  29. vec: 1
  30. 2
  31. 3
  32. 4
  33. 5
  34. magicFoo: 1
  35. 2
  36. 3
  37. 4
  38. 5
  39. 6
  40. 7
  41. 8
  42. 9
  43. foo2: 3, 4
  44. shiyanlou:2/ (master*) $                                             [13:46:38]
  45. shiyanlou:2/ (master*) $ g++ -std=c++17 2.05.structured.binding.cpp -o strubind
  46. 2.05.structured.binding.cpp: In function \u2018int main()\u2019:
  47. 2.05.structured.binding.cpp:19:10: error: expected unqualified-id before \u2018[\u2019 token
  48.      auto [x, y, z] = f();
  49.           ^
  50. 2.05.structured.binding.cpp:20:18: error: \u2018x\u2019 was not declared in this scope
  51.      std::cout << x << ", " << y << ", " << z << std::endl;
  52.                   ^
  53. 2.05.structured.binding.cpp:20:31: error: \u2018y\u2019 was not declared in this scope
  54.      std::cout << x << ", " << y << ", " << z << std::endl;
  55.                                ^
  56. 2.05.structured.binding.cpp:20:44: error: \u2018z\u2019 was not declared in this scope
  57.      std::cout << x << ", " << y << ", " << z << std::endl;
  58.                                             ^
  59. shiyanlou:2/ (master*) $ g++ -std=c++17 2.05.structured.binding.cpp -g -Wall -Wno-unused-variable -pthread -o strubind
  60. 2.05.structured.binding.cpp: In function \u2018int main()\u2019:
  61. 2.05.structured.binding.cpp:19:10: error: expected unqualified-id before \u2018[\u2019 token
  62.      auto [x, y, z] = f();
  63.           ^
  64. 2.05.structured.binding.cpp:20:18: error: \u2018x\u2019 was not declared in this scope
  65.      std::cout << x << ", " << y << ", " << z << std::endl;
  66.                   ^
  67. 2.05.structured.binding.cpp:20:31: error: \u2018y\u2019 was not declared in this scope
  68.      std::cout << x << ", " << y << ", " << z << std::endl;
  69.                                ^
  70. 2.05.structured.binding.cpp:20:44: error: \u2018z\u2019 was not declared in this scope
  71.      std::cout << x << ", " << y << ", " << z << std::endl;
  72.                                             ^
  73. shiyanlou:2/ (master*) $ g++ -std=c++17 2.05.structured.binding.cpp -o strubind
  74. 2.05.structured.binding.cpp: In function \u2018int main()\u2019:
  75. 2.05.structured.binding.cpp:19:10: error: declaration of \u2018auto x\u2019 has no initializer
  76.      auto x, y, z;
  77.           ^
  78. 2.05.structured.binding.cpp:19:13: error: declaration of \u2018auto y\u2019 has no initializer
  79.      auto x, y, z;
  80.              ^
  81. 2.05.structured.binding.cpp:19:16: error: declaration of \u2018auto z\u2019 has no initializer
  82.      auto x, y, z;
  83.                 ^
  84. 2.05.structured.binding.cpp: In lambda function:
  85. 2.05.structured.binding.cpp:20:15: error: expected \u2018{\u2019 before \u2018=\u2019 token
  86.      [x, y, z] = f();
  87.                ^
  88. 2.05.structured.binding.cpp: In function \u2018int main()\u2019:
  89. 2.05.structured.binding.cpp:20:15: error: no match for \u2018operator=\u2019 (operand types are \u2018main()::<lambda()>\u2019 and \u2018std::tuple<int, double, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >\u2019)
  90. 2.05.structured.binding.cpp:20:13: note: candidate: main()::<lambda()>& main()::<lambda()>::operator=(const main()::<lambda()>&) <deleted>
  91.      [x, y, z] = f();
  92.              ^
  93. 2.05.structured.binding.cpp:20:13: note:   no known conversion for argument 1 from \u2018std::tuple<int, double, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >\u2019 to \u2018const main()::<lambda()>&\u2019
  94. shiyanlou:2/ (master*) $ g++ -std=c++17 2.05.structured.binding.cpp -o strubind
  95. 2.05.structured.binding.cpp: In function \u2018int main()\u2019:
  96. 2.05.structured.binding.cpp:20:6: error: expected identifier before \u2018auto\u2019
  97.      [auto x,auto y,auto z] = f();
  98.       ^
  99. 2.05.structured.binding.cpp:20:12: error: expected \u2018]\u2019 before \u2018,\u2019 token
  100.      [auto x,auto y,auto z] = f();
  101.             ^
  102. 2.05.structured.binding.cpp: In lambda function:
  103. 2.05.structured.binding.cpp:20:12: error: expected \u2018{\u2019 before \u2018,\u2019 token
  104. 2.05.structured.binding.cpp: In function \u2018int main()\u2019:
  105. 2.05.structured.binding.cpp:20:13: error: expected primary-expression before \u2018auto\u2019
  106.      [auto x,auto y,auto z] = f();
  107.              ^
  108. 2.05.structured.binding.cpp:21:18: error: \u2018x\u2019 was not declared in this scope
  109.      std::cout << x << ", " << y << ", " << z << std::endl;
  110.                   ^
  111. 2.05.structured.binding.cpp:21:31: error: \u2018y\u2019 was not declared in this scope
  112.      std::cout << x << ", " << y << ", " << z << std::endl;
  113.                                ^
  114. 2.05.structured.binding.cpp:21:44: error: \u2018z\u2019 was not declared in this scope
  115.      std::cout << x << ", " << y << ", " << z << std::endl;
  116.                                             ^
  117. shiyanlou:2/ (master*) $ g++ -std=c++17 2.05.structured.binding.cpp -g -Wall -Wno-unused-variable -pthread -o strubind
  118. 2.05.structured.binding.cpp: In function \u2018int main()\u2019:
  119. 2.05.structured.binding.cpp:20:6: error: expected identifier before \u2018auto\u2019
  120.      [auto x, auto y, auto z] = f();
  121.       ^
  122. 2.05.structured.binding.cpp:20:12: error: expected \u2018]\u2019 before \u2018,\u2019 token
  123.      [auto x, auto y, auto z] = f();
  124.             ^
  125. 2.05.structured.binding.cpp: In lambda function:
  126. 2.05.structured.binding.cpp:20:12: error: expected \u2018{\u2019 before \u2018,\u2019 token
  127. 2.05.structured.binding.cpp: In function \u2018int main()\u2019:
  128. 2.05.structured.binding.cpp:20:14: error: expected primary-expression before \u2018auto\u2019
  129.      [auto x, auto y, auto z] = f();
  130.               ^
  131. 2.05.structured.binding.cpp:21:18: error: \u2018x\u2019 was not declared in this scope
  132.      std::cout << x << ", " << y << ", " << z << std::endl;
  133.                   ^
  134. 2.05.structured.binding.cpp:21:31: error: \u2018y\u2019 was not declared in this scope
  135.      std::cout << x << ", " << y << ", " << z << std::endl;
  136.                                ^
  137. 2.05.structured.binding.cpp:21:44: error: \u2018z\u2019 was not declared in this scope
  138.      std::cout << x << ", " << y << ", " << z << std::endl;
  139.                                             ^
  140. shiyanlou:2/ (master*) $ g++ -std=c++17 2.05.structured.binding.cpp -o strubind
  141. 2.05.structured.binding.cpp: In function \u2018int main()\u2019:
  142. 2.05.structured.binding.cpp:20:6: error: expected identifier before \u2018auto\u2019
  143.      [auto x, auto y, auto z] = f();
  144.       ^
  145. 2.05.structured.binding.cpp:20:12: error: expected \u2018]\u2019 before \u2018,\u2019 token
  146.      [auto x, auto y, auto z] = f();
  147.             ^
  148. 2.05.structured.binding.cpp: In lambda function:
  149. 2.05.structured.binding.cpp:20:12: error: expected \u2018{\u2019 before \u2018,\u2019 token
  150. 2.05.structured.binding.cpp: In function \u2018int main()\u2019:
  151. 2.05.structured.binding.cpp:20:14: error: expected primary-expression before \u2018auto\u2019
  152.      [auto x, auto y, auto z] = f();
  153.               ^
  154. 2.05.structured.binding.cpp:21:18: error: \u2018x\u2019 was not declared in this scope
  155.      std::cout << x << ", " << y << ", " << z << std::endl;
  156.                   ^
  157. 2.05.structured.binding.cpp:21:31: error: \u2018y\u2019 was not declared in this scope
  158.      std::cout << x << ", " << y << ", " << z << std::endl;
  159.                                ^
  160. 2.05.structured.binding.cpp:21:44: error: \u2018z\u2019 was not declared in this scope
  161.      std::cout << x << ", " << y << ", " << z << std::endl;
  162.                                             ^
  163. shiyanlou:2/ (master*) $ g++ -std=c++17 2.05.structured.binding.cpp -o strubind
  164. 2.05.structured.binding.cpp: In function \u2018int main()\u2019:
  165. 2.05.structured.binding.cpp:21:17: error: inconsistent deduction for \u2018auto\u2019: \u2018int\u2019 and then \u2018double\u2019
  166.      auto x=0, y=0.1, z="123";
  167.                  ^
  168. 2.05.structured.binding.cpp:21:24: error: inconsistent deduction for \u2018auto\u2019: \u2018int\u2019 and then \u2018const char*\u2019
  169.      auto x=0, y=0.1, z="123";
  170.                         ^
  171. 2.05.structured.binding.cpp: In lambda function:
  172. 2.05.structured.binding.cpp:23:15: error: expected \u2018{\u2019 before \u2018=\u2019 token
  173.      [x, y, z] = f();
  174.                ^
  175. 2.05.structured.binding.cpp: In function \u2018int main()\u2019:
  176. 2.05.structured.binding.cpp:23:15: error: no match for \u2018operator=\u2019 (operand types are \u2018main()::<lambda()>\u2019 and \u2018std::tuple<int, double, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >\u2019)
  177. 2.05.structured.binding.cpp:23:13: note: candidate: main()::<lambda()>& main()::<lambda()>::operator=(const main()::<lambda()>&) <deleted>
  178.      [x, y, z] = f();
  179.              ^
  180. 2.05.structured.binding.cpp:23:13: note:   no known conversion for argument 1 from \u2018std::tuple<int, double, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >\u2019 to \u2018const main()::<lambda()>&\u2019
  181. shiyanlou:2/ (master*) $ g++ -std=c++17 2.05.structured.binding.cpp -o strubind
  182. 2.05.structured.binding.cpp: In lambda function:
  183. 2.05.structured.binding.cpp:25:15: error: expected \u2018{\u2019 before \u2018=\u2019 token
  184.      [x, y, z] = f();
  185.                ^
  186. 2.05.structured.binding.cpp: In function \u2018int main()\u2019:
  187. 2.05.structured.binding.cpp:25:15: error: no match for \u2018operator=\u2019 (operand types are \u2018main()::<lambda()>\u2019 and \u2018std::tuple<int, double, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >\u2019)
  188. 2.05.structured.binding.cpp:25:13: note: candidate: main()::<lambda()>& main()::<lambda()>::operator=(const main()::<lambda()>&) <deleted>
  189.      [x, y, z] = f();
  190.              ^
  191. 2.05.structured.binding.cpp:25:13: note:   no known conversion for argument 1 from \u2018std::tuple<int, double, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >\u2019 to \u2018const main()::<lambda()>&\u2019
  192. shiyanlou:2/ (master*) $ g++ -std=c++17 2.05.structured.binding.cpp -o strubind
  193. 2.05.structured.binding.cpp: In lambda function:
  194. 2.05.structured.binding.cpp:25:15: error: expected \u2018{\u2019 before \u2018=\u2019 token
  195.      [x, y, z] = f();
  196.                ^
  197. 2.05.structured.binding.cpp: In function \u2018int main()\u2019:
  198. 2.05.structured.binding.cpp:25:15: error: no match for \u2018operator=\u2019 (operand types are \u2018main()::<lambda()>\u2019 and \u2018std::tuple<int, double, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >\u2019)
  199. 2.05.structured.binding.cpp:25:13: note: candidate: main()::<lambda()>& main()::<lambda()>::operator=(const main()::<lambda()>&) <deleted>
  200.      [x, y, z] = f();
  201.              ^
  202. 2.05.structured.binding.cpp:25:13: note:   no known conversion for argument 1 from \u2018std::tuple<int, double, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >\u2019 to \u2018const main()::<lambda()>&\u2019
  203. shiyanlou:2/ (master*) $ g++ -std=c++17 2.05.structured.binding.cpp -o strubind
  204. 2.05.structured.binding.cpp: In function \u2018int main()\u2019:
  205. 2.05.structured.binding.cpp:25:16: error: the value of \u2018x\u2019 is not usable in a constant expression
  206.      std::tuple<x, y, z> = f();
  207.                 ^
  208. 2.05.structured.binding.cpp:21:10: note: \u2018int x\u2019 is not const
  209.      auto x=0; 
  210.           ^
  211. 2.05.structured.binding.cpp:25:19: error: the value of \u2018y\u2019 is not usable in a constant expression
  212.      std::tuple<x, y, z> = f();
  213.                    ^
  214. 2.05.structured.binding.cpp:22:10: note: \u2018y\u2019 was not declared \u2018constexpr\u2019
  215.      auto y=0.1;
  216.           ^
  217. 2.05.structured.binding.cpp:25:22: error: the value of \u2018z\u2019 is not usable in a constant expression
  218.      std::tuple<x, y, z> = f();
  219.                       ^
  220. 2.05.structured.binding.cpp:23:10: note: \u2018z\u2019 was not declared \u2018constexpr\u2019
  221.      auto z="123";
  222.           ^
  223. 2.05.structured.binding.cpp:25:23: error: type/value mismatch at argument 1 in template parameter list for \u2018template<class ...> class std::tuple\u2019
  224.      std::tuple<x, y, z> = f();
  225.                        ^
  226. 2.05.structured.binding.cpp:25:23: note:   expected a type, got \u2018x\u2019
  227. 2.05.structured.binding.cpp:25:23: error: type/value mismatch at argument 1 in template parameter list for \u2018template<class ...> class std::tuple\u2019
  228. 2.05.structured.binding.cpp:25:23: note:   expected a type, got \u2018y\u2019
  229. 2.05.structured.binding.cpp:25:23: error: type/value mismatch at argument 1 in template parameter list for \u2018template<class ...> class std::tuple\u2019
  230. 2.05.structured.binding.cpp:25:23: note:   expected a type, got \u2018z\u2019
  231. 2.05.structured.binding.cpp:25:25: error: expected unqualified-id before \u2018=\u2019 token
  232.      std::tuple<x, y, z> = f();
  233.                          ^
  234. shiyanlou:2/ (master*) $ g++ -std=c++17 2.05.structured.binding.cpp -o strubind
  235. 2.05.structured.binding.cpp: In function \u2018int main()\u2019:
  236. 2.05.structured.binding.cpp:25:15: error: cannot convert \u2018std::tuple<int, double, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >\u2019 to \u2018const char*\u2019 in assignment
  237.      (x, y, z) = f();
  238.                ^
  239. shiyanlou:2/ (master*) $ g++ -std=c++17 2.05.structured.binding.cpp -o strubind
  240. 2.05.structured.binding.cpp: In function \u2018int main()\u2019:
  241. 2.05.structured.binding.cpp:25:15: error: no match for \u2018operator=\u2019 (operand types are \u2018std::__cxx11::string {aka std::__cxx11::basic_string<char>}\u2019 and \u2018std::tuple<int, double, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >\u2019)
  242.      (x, y, z) = f();
  243.                ^
  244. In file included from /usr/include/c++/5/string:52:0,
  245.                  from /usr/include/c++/5/bits/locale_classes.h:40,
  246.                  from /usr/include/c++/5/bits/ios_base.h:41,
  247.                  from /usr/include/c++/5/ios:42,
  248.                  from /usr/include/c++/5/ostream:38,
  249.                  from /usr/include/c++/5/iostream:39,
  250.                  from 2.05.structured.binding.cpp:10:
  251. /usr/include/c++/5/bits/basic_string.h:550:7: note: candidate: std::__cxx11::basic_string<_CharT, _Traits, _Alloc>& std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::operator=(const std::__cxx11::basic_string<_CharT, _Traits, _Alloc>&) [with _CharT = char; _Traits = std::char_traits<char>; _Alloc = std::allocator<char>]
  252.        operator=(const basic_string& __str)
  253.        ^
  254. /usr/include/c++/5/bits/basic_string.h:550:7: note:   no known conversion for argument 1 from \u2018std::tuple<int, double, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >\u2019 to \u2018const std::__cxx11::basic_string<char>&\u2019
  255. /usr/include/c++/5/bits/basic_string.h:558:7: note: candidate: std::__cxx11::basic_string<_CharT, _Traits, _Alloc>& std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::operator=(const _CharT*) [with _CharT = char; _Traits = std::char_traits<char>; _Alloc = std::allocator<char>]
  256.        operator=(const _CharT* __s)
  257.        ^
  258. /usr/include/c++/5/bits/basic_string.h:558:7: note:   no known conversion for argument 1 from \u2018std::tuple<int, double, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >\u2019 to \u2018const char*\u2019
  259. /usr/include/c++/5/bits/basic_string.h:569:7: note: candidate: std::__cxx11::basic_string<_CharT, _Traits, _Alloc>& std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::operator=(_CharT) [with _CharT = char; _Traits = std::char_traits<char>; _Alloc = std::allocator<char>]
  260.        operator=(_CharT __c)
  261.        ^
  262. /usr/include/c++/5/bits/basic_string.h:569:7: note:   no known conversion for argument 1 from \u2018std::tuple<int, double, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >\u2019 to \u2018char\u2019
  263. /usr/include/c++/5/bits/basic_string.h:587:7: note: candidate: std::__cxx11::basic_string<_CharT, _Traits, _Alloc>& std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::operator=(std::__cxx11::basic_string<_CharT, _Traits, _Alloc>&&) [with _CharT = char; _Traits = std::char_traits<char>; _Alloc = std::allocator<char>]
  264.        operator=(basic_string&& __str)
  265.        ^
  266. /usr/include/c++/5/bits/basic_string.h:587:7: note:   no known conversion for argument 1 from \u2018std::tuple<int, double, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >\u2019 to \u2018std::__cxx11::basic_string<char>&&\u2019
  267. /usr/include/c++/5/bits/basic_string.h:598:7: note: candidate: std::__cxx11::basic_string<_CharT, _Traits, _Alloc>& std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::operator=(std::initializer_list<_Tp>) [with _CharT = char; _Traits = std::char_traits<char>; _Alloc = std::allocator<char>]
  268.        operator=(initializer_list<_CharT> __l)
  269.        ^
  270. /usr/include/c++/5/bits/basic_string.h:598:7: note:   no known conversion for argument 1 from \u2018std::tuple<int, double, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >\u2019 to \u2018std::initializer_list<char>\u2019
  271. shiyanlou:2/ (master*) $ g++ -std=c++17 2.05.structured.binding.cpp -o strubind
  272. 2.05.structured.binding.cpp: In lambda function:
  273. 2.05.structured.binding.cpp:25:15: error: expected \u2018{\u2019 before \u2018=\u2019 token
  274.      [x, y, z] = f();
  275.                ^
  276. 2.05.structured.binding.cpp: In function \u2018int main()\u2019:
  277. 2.05.structured.binding.cpp:25:15: error: no match for \u2018operator=\u2019 (operand types are \u2018main()::<lambda()>\u2019 and \u2018std::tuple<int, double, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >\u2019)
  278. 2.05.structured.binding.cpp:25:13: note: candidate: main()::<lambda()>& main()::<lambda()>::operator=(const main()::<lambda()>&) <deleted>
  279.      [x, y, z] = f();
  280.              ^
  281. 2.05.structured.binding.cpp:25:13: note:   no known conversion for argument 1 from \u2018std::tuple<int, double, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >\u2019 to \u2018const main()::<lambda()>&\u2019
  282. shiyanlou:2/ (master*) $ g++ -std=c++17 2.05.structured.binding.cpp -o strubind
  283. shiyanlou:2/ (master*) $ ./strubind                                  [14:13:51]
  284. 0, 0.1, 123
  285. 0, 0.1, 123
  286. shiyanlou:2/ (master*) $ g++ -std=c++17 2.05.structured.binding.cpp -o strubind
  287. 2.05.structured.binding.cpp: In function \u2018int main()\u2019:
  288. 2.05.structured.binding.cpp:25:16: error: the value of \u2018x\u2019 is not usable in a constant expression
  289.      std::tuple<x, y, z> = f();
  290.                 ^
  291. 2.05.structured.binding.cpp:21:9: note: \u2018int x\u2019 is not const
  292.      int x=0; 
  293.          ^
  294. 2.05.structured.binding.cpp:25:19: error: the value of \u2018y\u2019 is not usable in a constant expression
  295.      std::tuple<x, y, z> = f();
  296.                    ^
  297. 2.05.structured.binding.cpp:22:12: note: \u2018y\u2019 was not declared \u2018constexpr\u2019
  298.      double y=0.1;
  299.             ^
  300. 2.05.structured.binding.cpp:25:22: error: the value of \u2018z\u2019 is not usable in a constant expression
  301.      std::tuple<x, y, z> = f();
  302.                       ^
  303. 2.05.structured.binding.cpp:23:17: note: \u2018z\u2019 was not declared \u2018constexpr\u2019
  304.      std::string z="123";
  305.                  ^
  306. 2.05.structured.binding.cpp:25:23: error: type/value mismatch at argument 1 in template parameter list for \u2018template<class ...> class std::tuple\u2019
  307.      std::tuple<x, y, z> = f();
  308.                        ^
  309. 2.05.structured.binding.cpp:25:23: note:   expected a type, got \u2018x\u2019
  310. 2.05.structured.binding.cpp:25:23: error: type/value mismatch at argument 1 in template parameter list for \u2018template<class ...> class std::tuple\u2019
  311. 2.05.structured.binding.cpp:25:23: note:   expected a type, got \u2018y\u2019
  312. 2.05.structured.binding.cpp:25:23: error: type/value mismatch at argument 1 in template parameter list for \u2018template<class ...> class std::tuple\u2019
  313. 2.05.structured.binding.cpp:25:23: note:   expected a type, got \u2018z\u2019
  314. 2.05.structured.binding.cpp:25:25: error: expected unqualified-id before \u2018=\u2019 token
  315.      std::tuple<x, y, z> = f();
  316.                          ^
  317. shiyanlou:2/ (master*) $ g++ -std=c++17 2.05.structured.binding.cpp -o strubind
  318. 2.05.structured.binding.cpp: In function \u2018int main()\u2019:
  319. 2.05.structured.binding.cpp:25:5: error: expected primary-expression before \u2018<\u2019 token
  320.      <x, y, z> = f();
  321.      ^
  322. 2.05.structured.binding.cpp:25:15: error: expected primary-expression before \u2018=\u2019 token
  323.      <x, y, z> = f();
  324.                ^
  325. shiyanlou:2/ (master*) $ g++ -std=c++17 2.05.structured.binding.cpp -o strubind
  326. 2.05.structured.binding.cpp: In function \u2018int main()\u2019:
  327. 2.05.structured.binding.cpp:25:15: error: no match for \u2018operator=\u2019 (operand types are \u2018std::__cxx11::string {aka std::__cxx11::basic_string<char>}\u2019 and \u2018std::tuple<int, double, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >\u2019)
  328.      (x, y, z) = f();
  329.                ^
  330. In file included from /usr/include/c++/5/string:52:0,
  331.                  from /usr/include/c++/5/bits/locale_classes.h:40,
  332.                  from /usr/include/c++/5/bits/ios_base.h:41,
  333.                  from /usr/include/c++/5/ios:42,
  334.                  from /usr/include/c++/5/ostream:38,
  335.                  from /usr/include/c++/5/iostream:39,
  336.                  from 2.05.structured.binding.cpp:10:
  337. /usr/include/c++/5/bits/basic_string.h:550:7: note: candidate: std::__cxx11::basic_string<_CharT, _Traits, _Alloc>& std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::operator=(const std::__cxx11::basic_string<_CharT, _Traits, _Alloc>&) [with _CharT = char; _Traits = std::char_traits<char>; _Alloc = std::allocator<char>]
  338.        operator=(const basic_string& __str)
  339.        ^
  340. /usr/include/c++/5/bits/basic_string.h:550:7: note:   no known conversion for argument 1 from \u2018std::tuple<int, double, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >\u2019 to \u2018const std::__cxx11::basic_string<char>&\u2019
  341. /usr/include/c++/5/bits/basic_string.h:558:7: note: candidate: std::__cxx11::basic_string<_CharT, _Traits, _Alloc>& std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::operator=(const _CharT*) [with _CharT = char; _Traits = std::char_traits<char>; _Alloc = std::allocator<char>]
  342.        operator=(const _CharT* __s)
  343.        ^
  344. /usr/include/c++/5/bits/basic_string.h:558:7: note:   no known conversion for argument 1 from \u2018std::tuple<int, double, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >\u2019 to \u2018const char*\u2019
  345. /usr/include/c++/5/bits/basic_string.h:569:7: note: candidate: std::__cxx11::basic_string<_CharT, _Traits, _Alloc>& std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::operator=(_CharT) [with _CharT = char; _Traits = std::char_traits<char>; _Alloc = std::allocator<char>]
  346.        operator=(_CharT __c)
  347.        ^
  348. /usr/include/c++/5/bits/basic_string.h:569:7: note:   no known conversion for argument 1 from \u2018std::tuple<int, double, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >\u2019 to \u2018char\u2019
  349. /usr/include/c++/5/bits/basic_string.h:587:7: note: candidate: std::__cxx11::basic_string<_CharT, _Traits, _Alloc>& std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::operator=(std::__cxx11::basic_string<_CharT, _Traits, _Alloc>&&) [with _CharT = char; _Traits = std::char_traits<char>; _Alloc = std::allocator<char>]
  350.        operator=(basic_string&& __str)
  351.        ^
  352. /usr/include/c++/5/bits/basic_string.h:587:7: note:   no known conversion for argument 1 from \u2018std::tuple<int, double, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >\u2019 to \u2018std::__cxx11::basic_string<char>&&\u2019
  353. /usr/include/c++/5/bits/basic_string.h:598:7: note: candidate: std::__cxx11::basic_string<_CharT, _Traits, _Alloc>& std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::operator=(std::initializer_list<_Tp>) [with _CharT = char; _Traits = std::char_traits<char>; _Alloc = std::allocator<char>]
  354.        operator=(initializer_list<_CharT> __l)
  355.        ^
  356. /usr/include/c++/5/bits/basic_string.h:598:7: note:   no known conversion for argument 1 from \u2018std::tuple<int, double, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >\u2019 to \u2018std::initializer_list<char>\u2019
  357. shiyanlou:2/ (master*) $ g++ -std=c++17 2.05.structured.binding.cpp -o strubind
  358. 2.05.structured.binding.cpp: In function \u2018int main()\u2019:
  359. 2.05.structured.binding.cpp:25:13: error: expected \u2018;\u2019 before \u2018}\u2019 token
  360.      {x, y, z} = f();
  361.              ^
  362. 2.05.structured.binding.cpp:25:15: error: expected primary-expression before \u2018=\u2019 token
  363.      {x, y, z} = f();
  364.                ^
  365. shiyanlou:2/ (master*) $ g++ -std=c++17 2.05.structured.binding.cpp -o strubind
  366. 2.05.structured.binding.cpp: In lambda function:
  367. 2.05.structured.binding.cpp:25:15: error: expected \u2018{\u2019 before \u2018=\u2019 token
  368.      [x, y, z] = f();
  369.                ^
  370. 2.05.structured.binding.cpp: In function \u2018int main()\u2019:
  371. 2.05.structured.binding.cpp:25:15: error: no match for \u2018operator=\u2019 (operand types are \u2018main()::<lambda()>\u2019 and \u2018std::tuple<int, double, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >\u2019)
  372. 2.05.structured.binding.cpp:25:13: note: candidate: main()::<lambda()>& main()::<lambda()>::operator=(const main()::<lambda()>&) <deleted>
  373.      [x, y, z] = f();
  374.              ^
  375. 2.05.structured.binding.cpp:25:13: note:   no known conversion for argument 1 from \u2018std::tuple<int, double, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >\u2019 to \u2018const main()::<lambda()>&\u2019
  376. shiyanlou:2/ (master*) $ g++ -std=c++17 2.05.structured.binding.cpp -o strubind
  377. 2.05.structured.binding.cpp: In function \u2018int main()\u2019:
  378. 2.05.structured.binding.cpp:25:10: error: expected unqualified-id before \u2018[\u2019 token
  379.      auto [x, y, z] = f();
  380.           ^
  381. shiyanlou:2/ (master*) $ g++ -std=c++17 2.05.structured.binding.cpp -o strubind
  382. shiyanlou:2/ (master*) $ ./strubind                                  [14:22:38]
  383. 0, 0.1, 123
  384. 1, 2.3, 456
  385. shiyanlou:2/ (master*) $ gcc -v                                      [14:22:41]
  386. Using built-in specs.
  387. COLLECT_GCC=gcc
  388. COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-linux-gnu/5/lto-wrapper
  389. Target: x86_64-linux-gnu
  390. Configured with: ../src/configure -v --with-pkgversion='Ubuntu 5.4.0-6ubuntu1~16.04.9' --with-bugurl=file:///usr/share/doc/gcc-5/README.Bugs --enable-languages=c,ada,c++,java,go,d,fortran,objc,obj-c++ --prefix=/usr --program-suffix=-5 --enable-shared --enable-linker-build-id --libexecdir=/usr/lib --without-included-gettext --enable-threads=posix --libdir=/usr/lib --enable-nls --with-sysroot=/ --enable-clocale=gnu --enable-libstdcxx-debug --enable-libstdcxx-time=yes --with-default-libstdcxx-abi=new --enable-gnu-unique-object --disable-vtable-verify --enable-libmpx --enable-plugin --with-system-zlib --disable-browser-plugin --enable-java-awt=gtk --enable-gtk-cairo --with-java-home=/usr/lib/jvm/java-1.5.0-gcj-5-amd64/jre --enable-java-home --with-jvm-root-dir=/usr/lib/jvm/java-1.5.0-gcj-5-amd64 --with-jvm-jar-dir=/usr/lib/jvm-exports/java-1.5.0-gcj-5-amd64 --with-arch-directory=amd64 --with-ecj-jar=/usr/share/java/eclipse-ecj.jar --enable-objc-gc --enable-multiarch --disable-werror --with-arch-32=i686 --with-abi=m64 --with-multilib-list=m32,m64,mx32 --enable-multilib --with-tune=generic --enable-checking=release --build=x86_64-linux-gnu --host=x86_64-linux-gnu --target=x86_64-linux-gnu
  391. Thread model: posix
  392. gcc version 5.4.0 20160609 (Ubuntu 5.4.0-6ubuntu1~16.04.9) 
  393. shiyanlou:2/ (master*) $ g++ -v                                      [14:28:11]
  394. Using built-in specs.
  395. COLLECT_GCC=g++
  396. COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-linux-gnu/5/lto-wrapper
  397. Target: x86_64-linux-gnu
  398. Configured with: ../src/configure -v --with-pkgversion='Ubuntu 5.4.0-6ubuntu1~16.04.9' --with-bugurl=file:///usr/share/doc/gcc-5/README.Bugs --enable-languages=c,ada,c++,java,go,d,fortran,objc,obj-c++ --prefix=/usr --program-suffix=-5 --enable-shared --enable-linker-build-id --libexecdir=/usr/lib --without-included-gettext --enable-threads=posix --libdir=/usr/lib --enable-nls --with-sysroot=/ --enable-clocale=gnu --enable-libstdcxx-debug --enable-libstdcxx-time=yes --with-default-libstdcxx-abi=new --enable-gnu-unique-object --disable-vtable-verify --enable-libmpx --enable-plugin --with-system-zlib --disable-browser-plugin --enable-java-awt=gtk --enable-gtk-cairo --with-java-home=/usr/lib/jvm/java-1.5.0-gcj-5-amd64/jre --enable-java-home --with-jvm-root-dir=/usr/lib/jvm/java-1.5.0-gcj-5-amd64 --with-jvm-jar-dir=/usr/lib/jvm-exports/java-1.5.0-gcj-5-amd64 --with-arch-directory=amd64 --with-ecj-jar=/usr/share/java/eclipse-ecj.jar --enable-objc-gc --enable-multiarch --disable-werror --with-arch-32=i686 --with-abi=m64 --with-multilib-list=m32,m64,mx32 --enable-multilib --with-tune=generic --enable-checking=release --build=x86_64-linux-gnu --host=x86_64-linux-gnu --target=x86_64-linux-gnu
  399. Thread model: posix
  400. gcc version 5.4.0 20160609 (Ubuntu 5.4.0-6ubuntu1~16.04.9) 
  401. shiyanlou:2/ (master*) $                                             [14:28:26]

 

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