58 lines
1.5 KiB
C++
58 lines
1.5 KiB
C++
#pragma once
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#include "utils/iterator/composable.hpp"
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#include "utils/iterator/iterator_base.hpp"
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namespace iter
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{
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// Class which maps values returned by I iterator into value of type T with OP
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// function and ends when op return empty optional.
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// T - type of return value
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// I - iterator type
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// OP - type of mapper function. OP: V -> Option<T>
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template <class T, class I, class OP>
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class LimitedMap : public IteratorBase<T>,
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public Composable<T, LimitedMap<T, I, OP>>
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{
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public:
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LimitedMap() = delete;
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// LimitedMap operation is designed to be used in chained calls which
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// operate on a
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// iterator. LimitedMap will in that usecase receive other iterator by value
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// and
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// std::move is a optimization for it.
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LimitedMap(I &&iter, OP &&op) : iter(std::move(iter)), op(std::move(op)) {}
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LimitedMap(LimitedMap &&m) : iter(std::move(m.iter)), op(std::move(m.op)) {}
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~LimitedMap() final {}
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Option<T> next() final
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{
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auto item = iter.next();
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if (item.is_present()) {
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return op(item.take());
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} else {
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return Option<T>();
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}
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}
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Count count() final { return iter.count(); }
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private:
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I iter;
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OP op;
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};
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template <class I, class OP>
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auto make_limited_map(I &&iter, OP &&op)
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{
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// Compiler cant deduce type T. decltype is here to help with it.
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return LimitedMap<decltype(op(iter.next().take()).take()), I, OP>(
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std::move(iter), std::move(op));
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}
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}
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