1 #include <functional> 2 #include <string> 3 4 template <class _Tp> 5 struct is_transparent 6 { 7 private: 8 struct __two {char __lx; char __lxx;}; 9 template <class _Up> static __two __test(...); 10 template <class _Up> static char __test(typename _Up::is_transparent* = 0); 11 public: 12 static const bool value = sizeof(__test<_Tp>(0)) == 1; 13 }; 14 15 16 int main () { 17 #if _LIBCPP_STD_VER > 11 18 19 static_assert ( !is_transparent<std::less<int>>::value, "" ); 20 static_assert ( !is_transparent<std::less<std::string>>::value, "" ); 21 static_assert ( is_transparent<std::less<void>>::value, "" ); 22 static_assert ( is_transparent<std::less<>>::value, "" ); 23 24 static_assert ( !is_transparent<std::less_equal<int>>::value, "" ); 25 static_assert ( !is_transparent<std::less_equal<std::string>>::value, "" ); 26 static_assert ( is_transparent<std::less_equal<void>>::value, "" ); 27 static_assert ( is_transparent<std::less_equal<>>::value, "" ); 28 29 static_assert ( !is_transparent<std::equal_to<int>>::value, "" ); 30 static_assert ( !is_transparent<std::equal_to<std::string>>::value, "" ); 31 static_assert ( is_transparent<std::equal_to<void>>::value, "" ); 32 static_assert ( is_transparent<std::equal_to<>>::value, "" ); 33 34 static_assert ( !is_transparent<std::not_equal_to<int>>::value, "" ); 35 static_assert ( !is_transparent<std::not_equal_to<std::string>>::value, "" ); 36 static_assert ( is_transparent<std::not_equal_to<void>>::value, "" ); 37 static_assert ( is_transparent<std::not_equal_to<>>::value, "" ); 38 39 static_assert ( !is_transparent<std::greater<int>>::value, "" ); 40 static_assert ( !is_transparent<std::greater<std::string>>::value, "" ); 41 static_assert ( is_transparent<std::greater<void>>::value, "" ); 42 static_assert ( is_transparent<std::greater<>>::value, "" ); 43 44 static_assert ( !is_transparent<std::greater_equal<int>>::value, "" ); 45 static_assert ( !is_transparent<std::greater_equal<std::string>>::value, "" ); 46 static_assert ( is_transparent<std::greater_equal<void>>::value, "" ); 47 static_assert ( is_transparent<std::greater_equal<>>::value, "" ); 48 49 #endif 50 51 return 0; 52 } 53