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42 lines
1.4 KiB
42 lines
1.4 KiB
/*
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* Copyright (C) 2011 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#ifndef ART_LIBARTBASE_BASE_STL_UTIL_IDENTITY_H_
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#define ART_LIBARTBASE_BASE_STL_UTIL_IDENTITY_H_
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namespace art {
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// Use to suppress type deduction for a function argument.
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// See std::identity<> for more background:
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// http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2005/n1856.html#20.2.2 - move/forward helpers
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//
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// e.g. "template <typename X> void bar(identity<X>::type foo);
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// bar(5); // compilation error
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// bar<int>(5); // ok
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// or "template <typename T> void foo(T* x, typename Identity<T*>::type y);
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// Base b;
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// Derived d;
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// foo(&b, &d); // Use implicit Derived* -> Base* conversion.
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// If T was deduced from both &b and &d, there would be a mismatch, i.e. deduction failure.
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template <typename T>
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struct Identity {
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using type = T;
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};
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} // namespace art
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#endif // ART_LIBARTBASE_BASE_STL_UTIL_IDENTITY_H_
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