1 //===----------------------------------------------------------------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 
9 // UNSUPPORTED: c++98, c++03, c++11
10 #include <functional>
11 #include <string>
12 
13 template <class T>
14 struct is_transparent
15 {
16 private:
17     struct two {char lx; char lxx;};
18     template <class U> static two test(...);
19     template <class U> static char test(typename U::is_transparent* = 0);
20 public:
21     static const bool value = sizeof(test<T>(0)) == 1;
22 };
23 
24 
25 int main(int, char**)
26 {
27     static_assert ( !is_transparent<std::less<int>>::value, "" );
28     static_assert ( !is_transparent<std::less<std::string>>::value, "" );
29     static_assert (  is_transparent<std::less<void>>::value, "" );
30     static_assert (  is_transparent<std::less<>>::value, "" );
31 
32     static_assert ( !is_transparent<std::less_equal<int>>::value, "" );
33     static_assert ( !is_transparent<std::less_equal<std::string>>::value, "" );
34     static_assert (  is_transparent<std::less_equal<void>>::value, "" );
35     static_assert (  is_transparent<std::less_equal<>>::value, "" );
36 
37     static_assert ( !is_transparent<std::equal_to<int>>::value, "" );
38     static_assert ( !is_transparent<std::equal_to<std::string>>::value, "" );
39     static_assert (  is_transparent<std::equal_to<void>>::value, "" );
40     static_assert (  is_transparent<std::equal_to<>>::value, "" );
41 
42     static_assert ( !is_transparent<std::not_equal_to<int>>::value, "" );
43     static_assert ( !is_transparent<std::not_equal_to<std::string>>::value, "" );
44     static_assert (  is_transparent<std::not_equal_to<void>>::value, "" );
45     static_assert (  is_transparent<std::not_equal_to<>>::value, "" );
46 
47     static_assert ( !is_transparent<std::greater<int>>::value, "" );
48     static_assert ( !is_transparent<std::greater<std::string>>::value, "" );
49     static_assert (  is_transparent<std::greater<void>>::value, "" );
50     static_assert (  is_transparent<std::greater<>>::value, "" );
51 
52     static_assert ( !is_transparent<std::greater_equal<int>>::value, "" );
53     static_assert ( !is_transparent<std::greater_equal<std::string>>::value, "" );
54     static_assert (  is_transparent<std::greater_equal<void>>::value, "" );
55     static_assert (  is_transparent<std::greater_equal<>>::value, "" );
56 
57     return 0;
58 }
59