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  1. #include <iostream>
  2. #include <typeinfo>
  3. #include <utility>
  4. // for demangle:
  5. #include <cxxabi.h>
  6. #include <string>
  7. #include <memory>
  8. #include <cstdlib>
  9.  
  10.  
  11. template<template<class T, T...> class Container, typename T, T... t, T... s>
  12. constexpr Container<T, t..., s...>
  13. concat_arglists(Container<T, t...>, Container<T, s...>) {
  14. 	return {};
  15. }
  16.  
  17. // swap_pairs: Пустой лист
  18. template <template<class T, T...> class Container, typename T>
  19. constexpr Container<T> swap_pairs(Container<T>) { return {}; }
  20.  
  21. // swap_pairs: Лист из 1 элемента
  22. template <template<class T, T...> class Container, typename T, T t>
  23. constexpr Container<T, t> swap_pairs(Container<T, t>) { return {}; }
  24.  
  25. // swap_pairs: Лист из 2  более элементов
  26. template <template<class T, T...> class Container, typename T, T t1, T t2, T... ts>
  27. constexpr auto
  28. swap_pairs(Container<T, t1, t2, ts...>) {
  29. 	using head = Container<T, t2, t1>;
  30. 	using tail = decltype(swap_pairs(Container<T, ts...>{}));
  31. 	using list = decltype(concat_arglists(head{}, tail{}));
  32. 	return list{};
  33. }
  34.  
  35. std::string demangle(const char* mangled)
  36. {
  37.       int status;
  38.       std::unique_ptr<char[], void (*)(void*)> result(
  39.         abi::__cxa_demangle(mangled, 0, 0, &status), std::free);
  40.       return result.get() ? std::string(result.get()) : "error occurred";
  41. }
  42.  
  43. int main() {
  44. 	std::integer_sequence<int, 2, 1, 4, 3> a;
  45. 	std::integer_sequence<int, 4, 5, 2, 3, 1> b;
  46. 	auto c = concat_arglists(a, b);
  47. 	auto d = swap_pairs(c);
  48. 	std::cout << "a = " << demangle( typeid(a).name() ) << std::endl;
  49. 	std::cout << "b = " << demangle( typeid(b).name() ) << std::endl;
  50. 	std::cout << "c = " << demangle( typeid(c).name() ) << std::endl;
  51. 	std::cout << "d = " << demangle( typeid(d).name() ) << std::endl;
  52. 	return 0;
  53. }
  54.  
Success #stdin #stdout 0s 4416KB
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Standard input is empty
stdout
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a = std::integer_sequence<int, 2, 1, 4, 3>
b = std::integer_sequence<int, 4, 5, 2, 3, 1>
c = std::integer_sequence<int, 2, 1, 4, 3, 4, 5, 2, 3, 1>
d = std::integer_sequence<int, 1, 2, 3, 4, 5, 4, 3, 2, 1>
https://ideone.com/qxyr7T
language:
C++14 (gcc 8.3)
created:
7 years ago
visibility:
public

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