has_ostream_operator.h (1330B)
1 // Copyright 2023 The Abseil Authors 2 // 3 // Licensed under the Apache License, Version 2.0 (the "License"); 4 // you may not use this file except in compliance with the License. 5 // You may obtain a copy of the License at 6 // 7 // https://www.apache.org/licenses/LICENSE-2.0 8 // 9 // Unless required by applicable law or agreed to in writing, software 10 // distributed under the License is distributed on an "AS IS" BASIS, 11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 12 // See the License for the specific language governing permissions and 13 // limitations under the License. 14 15 #ifndef ABSL_STRINGS_HAS_OSTREAM_OPERATOR_H_ 16 #define ABSL_STRINGS_HAS_OSTREAM_OPERATOR_H_ 17 18 #include <ostream> 19 #include <type_traits> 20 #include <utility> 21 22 #include "absl/base/config.h" 23 24 namespace absl { 25 ABSL_NAMESPACE_BEGIN 26 27 // Detects if type `T` supports streaming to `std::ostream`s with `operator<<`. 28 29 template <typename T, typename = void> 30 struct HasOstreamOperator : std::false_type {}; 31 32 template <typename T> 33 struct HasOstreamOperator< 34 T, std::enable_if_t<std::is_same< 35 std::ostream&, decltype(std::declval<std::ostream&>() 36 << std::declval<const T&>())>::value>> 37 : std::true_type {}; 38 39 ABSL_NAMESPACE_END 40 } // namespace absl 41 42 #endif // ABSL_STRINGS_HAS_OSTREAM_OPERATOR_H_