| /* |
| * Copyright (C) 2015 The Android Open Source Project |
| * |
| * Licensed under the Apache License, Version 2.0 (the "License"); |
| * you may not use this file except in compliance with the License. |
| * You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| |
| #ifndef AAPT_UTIL_TYPETRAITS_H |
| #define AAPT_UTIL_TYPETRAITS_H |
| |
| #include <type_traits> |
| |
| namespace aapt { |
| |
| #define DEFINE_HAS_BINARY_OP_TRAIT(name, op) \ |
| template <typename T, typename U> \ |
| struct name { \ |
| template <typename V, typename W> \ |
| static constexpr decltype(std::declval<V>() op std::declval<W>(), bool()) \ |
| test(int) { \ |
| return true; \ |
| } \ |
| template <typename V, typename W> \ |
| static constexpr bool test(...) { \ |
| return false; \ |
| } \ |
| static constexpr bool value = test<T, U>(int()); \ |
| } |
| |
| DEFINE_HAS_BINARY_OP_TRAIT(has_eq_op, ==); |
| DEFINE_HAS_BINARY_OP_TRAIT(has_lt_op, <); |
| |
| /** |
| * Type trait that checks if two types can be equated (==) and compared (<). |
| */ |
| template <typename T, typename U> |
| struct is_comparable { |
| static constexpr bool value = |
| has_eq_op<T, U>::value && has_lt_op<T, U>::value; |
| }; |
| |
| } // namespace aapt |
| |
| #endif /* AAPT_UTIL_TYPETRAITS_H */ |