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 22 namespace 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()) \ 29 test(int) { \ 30 return true; \ 31 } \ 32 template <typename V, typename W> \ 33 static constexpr bool test(...) { \ 34 return false; \ 35 } \ 36 static constexpr bool value = test<T, U>(int()); \ 37 } 38 39 DEFINE_HAS_BINARY_OP_TRAIT(has_eq_op, ==); 40 DEFINE_HAS_BINARY_OP_TRAIT(has_lt_op, <); 41 42 /** 43 * Type trait that checks if two types can be equated (==) and compared (<). 44 */ 45 template <typename T, typename U> 46 struct is_comparable { 47 static constexpr bool value = 48 has_eq_op<T, U>::value && has_lt_op<T, U>::value; 49 }; 50 51 } // namespace aapt 52 53 #endif /* AAPT_UTIL_TYPETRAITS_H */ 54
