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  1. #include <iostream>
  2. #include <type_traits>
  3. #include <vector>
  4. #include <iostream>
  5. #include <set>
  6.  
  7. template<typename T, typename Iterator, typename=void>
  8. struct is_iterator_of_type: std::false_type {};
  9.  
  10. template<typename T, typename Iterator>
  11. struct is_iterator_of_type<
  12.     T,
  13. 	Iterator,
  14. 	typename std::enable_if<
  15. 		std::is_same<
  16. 			T,
  17. 			typename std::iterator_traits< Iterator >::value_type
  18. 		>::value
  19. 	>::type
  20. >: std::true_type {};
  21.  
  22. void test1() {
  23.   std::cout << is_iterator_of_type<int, std::vector<int>::iterator>::value << "\n";
  24. }
  25. template<typename T, typename Container>
  26. auto foo(Container const&) -> typename std::enable_if< is_iterator_of_type<T, typename Container::iterator>::value >::type
  27. {
  28. 	std::cout << "Container of int\n";
  29. }
  30. template<typename T>
  31. void foo(...)
  32. {
  33. 	std::cout << "No match\n";
  34. }
  35. void test2() {
  36.   std::vector<int> test;
  37. 	foo<int>(test);
  38. 	foo<int>(test.begin());
  39. 	foo<int>(std::set<int>());
  40. }
  41. template<typename Container>
  42. auto operator<<( std::ostream& stream, Container const& c ) ->
  43. 	typename std::enable_if< is_iterator_of_type<int, typename Container::iterator>::value, std::ostream& >::type
  44. {
  45. 	stream << "int container\n";
  46. }
  47. void test3() {
  48. 	std::vector<int> test;
  49. 	std::cout << test;
  50. 	std::set<int> bar;
  51. 	std::cout << bar;
  52. }
  53. template<typename Container>
  54. auto operator<<( std::ostream& stream, Container const& c ) ->
  55. 	typename std::enable_if< is_iterator_of_type<double, typename Container::iterator>::value, std::ostream& >::type
  56. {
  57. 	stream << "double container\n";
  58. }
  59. void test4() {
  60. 	std::vector<int> test;
  61. 	std::cout << test;
  62. 	std::set<int> bar;
  63. 	std::cout << bar;
  64. 	std::vector<double> dtest;
  65. 	std::cout << dtest;
  66. }
  67. void test5() {
  68. 	std::vector<bool> test;
  69. 	// does not compile (naturall):
  70. 	// std::cout << test;
  71. }
  72. template<typename Container>
  73. auto operator<<( std::ostream& stream, Container const& c ) ->
  74. 	typename std::enable_if< is_iterator_of_type<bool, typename Container::iterator>::value, std::ostream& >::type
  75. {
  76. 	stream << "bool container\n";
  77. }
  78. void test6() {
  79. 	std::vector<bool> test;
  80. 	// now compiles:
  81. 	std::cout << test;
  82. }
  83. int main() {
  84. 	test1();
  85. 	test2();
  86. 	test3();
  87. 	test4();
  88. 	test5();
  89. 	test6();
  90. }
  91.  
  92.  
Success #stdin #stdout 0s 2884KB
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stdin
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Standard input is empty
stdout
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1
Container of int
No match
Container of int
int container
int container
int container
int container
double container
bool container
https://ideone.com/lMUF4i
language:
C++14 (gcc 8.3)
created:
11 years ago
visibility:
public

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