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| 1 | +#pragma once |
| 2 | + |
| 3 | +#if defined(__GNUC__) && !defined(__clang__) |
| 4 | +#pragma message("ttl::experimental::zip is error-prone, use with care!") |
| 5 | +#endif |
| 6 | + |
| 7 | +#include <array> |
| 8 | +#include <functional> |
| 9 | +#include <numeric> |
| 10 | +#include <tuple> |
| 11 | + |
| 12 | +namespace ttl |
| 13 | +{ |
| 14 | +namespace experimental |
| 15 | +{ |
| 16 | +namespace internal |
| 17 | +{ |
| 18 | +template <typename... Ts> |
| 19 | +class zipper_t |
| 20 | +{ |
| 21 | + static constexpr auto arity = sizeof...(Ts); |
| 22 | + |
| 23 | + const std::tuple<const Ts &...> ranges_; |
| 24 | + |
| 25 | + template <typename... Iters> |
| 26 | + class iterator |
| 27 | + { |
| 28 | + std::tuple<Iters...> is_; |
| 29 | + |
| 30 | + template <size_t... Is> |
| 31 | + auto operator*(std::index_sequence<Is...>) |
| 32 | + { |
| 33 | + return std::make_tuple(*std::get<Is>(is_)...); |
| 34 | + } |
| 35 | + |
| 36 | + template <typename... P> |
| 37 | + static void noop(const P &...) |
| 38 | + { |
| 39 | + } |
| 40 | + |
| 41 | + template <typename Iter> |
| 42 | + int incr(Iter &i) |
| 43 | + { |
| 44 | + ++i; |
| 45 | + return 0; |
| 46 | + } |
| 47 | + |
| 48 | + template <size_t... Is> |
| 49 | + void _advance(std::index_sequence<Is...>) |
| 50 | + { |
| 51 | + noop(incr(std::get<Is>(is_))...); |
| 52 | + } |
| 53 | + |
| 54 | + template <size_t... Is> |
| 55 | + bool neq(std::index_sequence<Is...>, const iterator &p) const |
| 56 | + { |
| 57 | + // TODO: expand the expression |
| 58 | + std::array<bool, arity> neqs( |
| 59 | + {(std::get<Is>(is_) != std::get<Is>(p.is_))...}); |
| 60 | + return std::accumulate(neqs.begin(), neqs.end(), false, |
| 61 | + std::logical_or<bool>()); |
| 62 | + } |
| 63 | + |
| 64 | + public: |
| 65 | + iterator(const Iters &... i) : is_(i...) {} |
| 66 | + |
| 67 | + bool operator!=(const iterator &p) const |
| 68 | + { |
| 69 | + // return get<0>(is_) != get<0>(p.is_) || get<1>(is_) != |
| 70 | + // get<1>(p.is_); |
| 71 | + return neq(std::make_index_sequence<arity>(), p); |
| 72 | + } |
| 73 | + |
| 74 | + void operator++() |
| 75 | + { |
| 76 | + _advance(std::make_index_sequence<arity>()); |
| 77 | + // ++get<0>(is_), ++get<1>(is_); |
| 78 | + } |
| 79 | + |
| 80 | + auto operator*() |
| 81 | + { |
| 82 | + return (operator*)(std::make_index_sequence<arity>()); |
| 83 | + } |
| 84 | + }; |
| 85 | + |
| 86 | + template <typename... Iters> |
| 87 | + static iterator<Iters...> make_iterator(const Iters &... is) |
| 88 | + { |
| 89 | + return iterator<Iters...>(is...); |
| 90 | + } |
| 91 | + |
| 92 | + template <size_t... Is> |
| 93 | + auto begin(std::index_sequence<Is...>) const |
| 94 | + { |
| 95 | + return make_iterator(std::get<Is>(ranges_).begin()...); |
| 96 | + } |
| 97 | + |
| 98 | + template <size_t... Is> |
| 99 | + auto end(std::index_sequence<Is...>) const |
| 100 | + { |
| 101 | + return make_iterator(std::get<Is>(ranges_).end()...); |
| 102 | + } |
| 103 | + |
| 104 | + public: |
| 105 | + zipper_t(const Ts &... ranges) : ranges_(ranges...) {} |
| 106 | + |
| 107 | + auto begin() const { return begin(std::make_index_sequence<arity>()); } |
| 108 | + |
| 109 | + auto end() const { return end(std::make_index_sequence<arity>()); } |
| 110 | +}; |
| 111 | + |
| 112 | +template <typename... Ts> |
| 113 | +zipper_t<Ts...> zip(const Ts &... ranges) |
| 114 | +{ |
| 115 | + return zipper_t<Ts...>(ranges...); |
| 116 | +} |
| 117 | +} // namespace internal |
| 118 | +} // namespace experimental |
| 119 | +} // namespace ttl |
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