58 lines
1.6 KiB
C++
58 lines
1.6 KiB
C++
/*
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* Copyright 2014 Google Inc. All rights reserved.
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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 FRUIT_META_LIST_H
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#define FRUIT_META_LIST_H
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#include <fruit/impl/meta/basics.h>
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#include <fruit/impl/meta/logical_operations.h>
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#include <fruit/impl/meta/numeric_operations.h>
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#include <functional>
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namespace fruit {
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namespace impl {
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namespace meta {
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// List ::= EmptyList | Cons<T, List>
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struct EmptyList {};
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template <typename T, typename Tail>
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struct Cons {};
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// TODO: Consider inlining to improve performance.
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// If L is a list containing T1,...,Tn this calculates F(InitialValue, F(T1, F(..., F(Tn) ...))).
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struct FoldList {
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template <typename L, typename F, typename InitialValue>
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struct apply;
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template <typename F, typename InitialValue>
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struct apply<EmptyList, F, InitialValue> {
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using type = InitialValue;
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};
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template <typename Head, typename Tail, typename F, typename InitialValue>
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struct apply<Cons<Head, Tail>, F, InitialValue> {
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using type = FoldList(Tail, F, F(InitialValue, Head));
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};
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};
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} // namespace meta
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} // namespace impl
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} // namespace fruit
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#endif // FRUIT_META_LIST_H
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