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  1. #include <iostream>
  2. #include <tuple>
  3. #include <string>
  4. #include <cassert>
  5.  
  6. using namespace std;
  7.  
  8. struct A {
  9. 	A() = default;
  10. 	A(int v) : value_(v) {}
  11. 	int hash() const { return value_; }
  12.  
  13. 	int value_;
  14. };
  15.  
  16. struct B {
  17. 	B() = default;
  18. 	B(string v) : value_(v) {}
  19. 	int hash() const { return value_.size(); }
  20.  
  21. 	string value_;
  22. };
  23.  
  24.  
  25. template<typename T> class hash_getter {
  26. public:
  27. 	hash_getter(T & t): kontener_(t) {}
  28.  
  29. 	template<typename Y, int I> Y & get_type() { return std::get<I>(kontener_); }
  30.  
  31. 	int get_hash(int index) {
  32. 		switch (index) {
  33. 			case 0: return std::get<0>(kontener_).hash();
  34. 			case 1: return std::get<1>(kontener_).hash();
  35. 			default: assert(!"dupa");
  36. 		}
  37. 	}
  38.  
  39. private:
  40. 	T& kontener_;
  41. };
  42.  
  43. int main() {
  44. 	tuple<A, B> k(A(12), B("foo"));
  45.  
  46. 	hash_getter<decltype(k)> hasher(k);
  47.  
  48. 	// tutaj starczy wiedza podczas kompilacji
  49. 	cout << hasher.get_type<B, 1>().value_ << endl;
  50.  
  51. 	int index;
  52. 	cout << "chcesz hash ktorego obiektu?: ";
  53. 	cin >> index;
  54.  
  55. 	cout << index << " hash " << hasher.get_hash(index) << endl;
  56.  
  57. 	return 0;
  58. }
Success #stdin #stdout 0s 3460KB
comments (?)
stdin 
1
stdout 
foo
chcesz hash ktorego obiektu?: 1 hash 3
https://ideone.com/CjtmHZ
language:
C++14 (gcc 8.3)
created:
10 years ago
visibility:
public

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