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  1. #include <iostream>
  2. #include <iterator>
  3.  
  4. struct Generator : std::iterator<std::input_iterator_tag, int>
  5. {
  6. 	Generator &operator++()
  7. 	{
  8. 		++n;
  9. 		gen = false;
  10. 	}
  11. 	Generator operator++(int)
  12. 	{
  13. 		Generator t = *this;
  14. 		++*this;
  15. 		return t;
  16. 	}
  17. 	bool operator==(Generator const &g)
  18. 	{
  19. 		return n == g.n;
  20. 	}
  21. 	bool operator!=(Generator const &g)
  22. 	{
  23. 		return n != g.n;
  24. 	}
  25. 	int operator*()
  26. 	{
  27. 		if(!gen)
  28. 		{
  29. 			val = n*n*n;
  30. 			gen = true;
  31. 			std::cout << "Generated " << n << " -> " << val << std::endl;
  32. 		}
  33. 		return val;
  34. 	}
  35. private:
  36. 	int n = 0;
  37. 	bool gen = false;
  38. 	int val;
  39. };
  40.  
  41. int main()
  42. {
  43. 	Generator g;
  44. 	for(unsigned i = 0; i < 100; ++i, ++g)
  45. 	{
  46. 		if(i%3 == 0)
  47. 		{
  48. 			std::cout << *g << std::endl;
  49. 		}
  50. 	}
  51. }
  52.  
Success #stdin #stdout 0s 3340KB
comments (?)
stdin 
Standard input is empty
stdout 
Generated 0 -> 0
0
Generated 3 -> 27
27
Generated 6 -> 216
216
Generated 9 -> 729
729
Generated 12 -> 1728
1728
Generated 15 -> 3375
3375
Generated 18 -> 5832
5832
Generated 21 -> 9261
9261
Generated 24 -> 13824
13824
Generated 27 -> 19683
19683
Generated 30 -> 27000
27000
Generated 33 -> 35937
35937
Generated 36 -> 46656
46656
Generated 39 -> 59319
59319
Generated 42 -> 74088
74088
Generated 45 -> 91125
91125
Generated 48 -> 110592
110592
Generated 51 -> 132651
132651
Generated 54 -> 157464
157464
Generated 57 -> 185193
185193
Generated 60 -> 216000
216000
Generated 63 -> 250047
250047
Generated 66 -> 287496
287496
Generated 69 -> 328509
328509
Generated 72 -> 373248
373248
Generated 75 -> 421875
421875
Generated 78 -> 474552
474552
Generated 81 -> 531441
531441
Generated 84 -> 592704
592704
Generated 87 -> 658503
658503
Generated 90 -> 729000
729000
Generated 93 -> 804357
804357
Generated 96 -> 884736
884736
Generated 99 -> 970299
970299
https://ideone.com/wUasfM
language:
C++14 (gcc 8.3)
created:
10 years ago
visibility:
public

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