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1 | #pragma once | ||
2 | |||
3 | #include <utility> | ||
4 | |||
5 | #include "../Common.h" | ||
6 | |||
7 | namespace CXXIter { | ||
8 | |||
9 | // ################################################################################################ | ||
10 | // TAKE WHILE | ||
11 | // ################################################################################################ | ||
12 | namespace op { | ||
13 | /** @private */ | ||
14 | template<typename TChainInput> | ||
15 | class [[nodiscard(CXXITER_CHAINER_NODISCARD_WARNING)]] TakeN : public IterApi<TakeN<TChainInput>> { | ||
16 | friend struct trait::Iterator<TakeN<TChainInput>>; | ||
17 | private: | ||
18 | TChainInput input; | ||
19 | size_t n; | ||
20 | size_t remaining; | ||
21 | public: | ||
22 | 27 | constexpr TakeN(TChainInput&& input, size_t n) : input(std::move(input)), n(n), remaining(n) {} | |
23 | }; | ||
24 | } | ||
25 | // ------------------------------------------------------------------------------------------------ | ||
26 | /** @private */ | ||
27 | template<typename TChainInput> | ||
28 | struct trait::Iterator<op::TakeN<TChainInput>> { | ||
29 | using ChainInputIterator = trait::Iterator<TChainInput>; | ||
30 | using InputItem = typename TChainInput::Item; | ||
31 | // CXXIter Interface | ||
32 | using Self = op::TakeN<TChainInput>; | ||
33 | using Item = InputItem; | ||
34 | |||
35 | 139 | static constexpr inline IterValue<Item> next(Self& self) { | |
36 |
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139 | if(self.remaining == 0) [[unlikely]] { return {}; } |
37 |
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129 | auto item = ChainInputIterator::next(self.input); |
38 |
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129 | if(!item.has_value()) [[unlikely]] { return {}; } |
39 | 127 | self.remaining -= 1; | |
40 | 127 | return item; | |
41 | } | ||
42 | 11 | static constexpr inline SizeHint sizeHint(const Self& self) { | |
43 |
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11 | SizeHint input = ChainInputIterator::sizeHint(self.input); |
44 | return SizeHint( | ||
45 | 11 | std::min(input.lowerBound, self.n), | |
46 | 11 | SizeHint::upperBoundMin(input.upperBound, self.n) | |
47 |
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22 | ); |
48 | } | ||
49 | static constexpr inline size_t advanceBy(Self& self, size_t n) { | ||
50 | size_t skipN = ChainInputIterator::advanceby(self.input, n); | ||
51 | if(self.n < skipN) { self.n = 0; } else { self.n -= skipN; } | ||
52 | return skipN; | ||
53 | } | ||
54 | }; | ||
55 | /** @private */ | ||
56 | template<CXXIterExactSizeIterator TChainInput> | ||
57 | struct trait::ExactSizeIterator<op::TakeN<TChainInput>> { | ||
58 | 1 | static constexpr inline size_t size(const op::TakeN<TChainInput>& self) { | |
59 | 1 | return trait::Iterator<op::TakeN<TChainInput>>::sizeHint(self).lowerBound; | |
60 | } | ||
61 | }; | ||
62 | } | ||
63 |