1/*
2 * Copyright (C) 2015 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17#ifndef AAPT_UTIL_TYPETRAITS_H
18#define AAPT_UTIL_TYPETRAITS_H
19
20#include <type_traits>
21
22namespace aapt {
23
24#define DEFINE_HAS_BINARY_OP_TRAIT(name, op) \
25    template <typename T, typename U> \
26    struct name { \
27        template <typename V, typename W> \
28        static constexpr decltype(std::declval<V>() op std::declval<W>(), bool()) test(int) { \
29        return true; \
30    } \
31    template <typename V, typename W> \
32    static constexpr bool test(...) { \
33        return false; \
34    } \
35    static constexpr bool value = test<T, U>(int()); \
36}
37
38DEFINE_HAS_BINARY_OP_TRAIT(has_eq_op, ==);
39DEFINE_HAS_BINARY_OP_TRAIT(has_lt_op, <);
40
41/**
42 * Type trait that checks if two types can be equated (==) and compared (<).
43 */
44template <typename T, typename U>
45struct is_comparable {
46    static constexpr bool value = has_eq_op<T, U>::value && has_lt_op<T, U>::value;
47};
48
49} // namespace aapt
50
51#endif /* AAPT_UTIL_TYPETRAITS_H */
52