Library/Range/istream.hpp

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• Last update: 2025-07-06 21:41:14+09:00
• Include: #include "Library/Range/istream.hpp"

Depends on

• Library/Utility/Tuple.hpp
• Library/Utility/io.hpp

Verified with

• Test/DataStructure/RunLengthEncoding.test.cpp
• Test/Graph/Normal/StronglyConnectedComponents.test.cpp
• Test/Math/Convolution_and.test.cpp
• Test/Math/Math.test.cpp
• Test/Math/Math_dynamic.test.cpp
• Test/Math/Math_pow.test.cpp
• Test/Math/Math_pow_dynamic.test.cpp
• Test/Range/flatten.test.cpp

Code

#pragma once

#include <ranges>

#include "../Utility/io.hpp"

namespace mtd {
  namespace ranges {

    constexpr int _inf = 1e9;

    template <class... Args>
    struct istream_view
        : public std::ranges::view_interface<istream_view<Args...>> {
      class iterator {
        int count;
        std::tuple<Args...> val;

      public:
        using difference_type = int;
        using value_type = decltype(val);
        using iterator_concept = std::input_iterator_tag;

        constexpr iterator() = default;
        constexpr explicit iterator(int _count) : count(_count) {
          operator++();
        }

        constexpr auto operator*() const { return val; }
        constexpr auto& operator++() {
          --count;
          if (count >= 0) { val = io::in<Args...>(); }
          return *this;
        }
        constexpr auto operator++(int) { return ++*this; }

        constexpr auto operator==(const iterator& s) const {
          return count == s.count;
        }
        constexpr auto operator==(std::default_sentinel_t) const {
          return count < 0 || std::cin.eof() || std::cin.fail() ||
                 std::cin.bad();
        }
        constexpr friend auto operator==(std::default_sentinel_t s,
                                         const iterator& li) {
          return li == s;
        }
      };

      int count;

    public:
      constexpr explicit istream_view(int _count) : count(_count) {}
      constexpr explicit istream_view() : istream_view(_inf) {}
      constexpr auto begin() const { return iterator(count); }
      constexpr auto end() const { return std::default_sentinel; }
    };
  }  // namespace ranges

  namespace views {
    namespace __detail {
      template <typename... _Args>
      concept __can_istream_view = requires {
        ranges::istream_view(std::declval<_Args>()...);
      };
    }  // namespace __detail

    template <class... Args>
    struct _Istream {
      template <class... _Tp>
      requires __detail::__can_istream_view<_Tp...>
      constexpr auto operator() [[nodiscard]] (_Tp&&... __e) const {
        return ranges::istream_view<Args...>(std::forward<_Tp>(__e)...);
      }
    };

    template <class... Args>
    inline constexpr _Istream<Args...> istream{};
  }  // namespace views

}  // namespace mtd

#line 2 "Library/Range/istream.hpp"

#include <ranges>

#line 2 "Library/Utility/io.hpp"

#include <iostream>
#line 5 "Library/Utility/io.hpp"
#include <type_traits>
#include <vector>

#line 2 "Library/Utility/Tuple.hpp"

#include <functional>

namespace mtd {
  namespace util {
    template <class F, class T>
    constexpr auto tuple_transform(F&& f, T&& t) {
      return std::apply(
          [&]<class... Ts>(Ts&&... elems) {
            return std::tuple<std::invoke_result_t<F&, Ts>...>(
                std::invoke(f, std::forward<Ts>(elems))...);
          },
          std::forward<T>(t));
    }
    template <class F, class T>
    constexpr auto tuple_for_each(F&& f, T&& t) {
      std::apply(
          [&]<class... Ts>(Ts&&... elems) {
            (std::invoke(f, std::forward<Ts>(elems)), ...);
          },
          std::forward<T>(t));
    }
  }  // namespace util
}  // namespace mtd
#line 9 "Library/Utility/io.hpp"

namespace mtd {
  namespace io {

    namespace __details {
      template <typename T>
      concept is_vec = std::same_as<
          T, std::vector<typename T::value_type, typename T::allocator_type>>;
      template <typename T>
      concept is_mat = is_vec<T> && is_vec<typename T::value_type>;

    }  // namespace __details

    template <class T>
    constexpr auto _input() {
      T x;
      std::cin >> x;
      return x;
    }
    template <typename T>
    requires requires { typename std::tuple_size<T>::type; }
    constexpr auto _input() {
      T x;
      util::tuple_for_each([](auto&& i) { std::cin >> i; }, x);
      return x;
    }
    template <__details::is_vec T>
    constexpr auto _input(int n) {
      std::vector<typename T::value_type> v;
      v.reserve(n);
      for (auto i : std::views::iota(0, n)) {
        v.emplace_back(_input<typename T::value_type>());
      }
      return v;
    }
    template <__details::is_mat T>
    constexpr auto _input(int h, int w) {
      T mat;
      mat.reserve(h);
      for (auto i : std::views::iota(0, h)) {
        mat.emplace_back(_input<typename T::value_type>(w));
      }
      return mat;
    }

    template <int N, class Tuple, class T, class... Args, class... Sizes>
    constexpr auto _tuple_input(Tuple& t, Sizes... sizes);
    template <int N, class Tuple, __details::is_vec T, class... Args,
              class Size, class... Sizes>
    constexpr auto _tuple_input(Tuple& t, Size size, Sizes... sizes);
    template <int N, class Tuple, __details::is_mat T, class... Args,
              class Size, class... Sizes>
    constexpr auto _tuple_input(Tuple& t, Size size_h, Size size_w,
                                Sizes... sizes);

    template <int N, class Tuple, class T, class... Args, class... Sizes>
    constexpr auto _tuple_input(Tuple& t, Sizes... sizes) {
      std::get<N>(t) = _input<T>();
      if constexpr (sizeof...(Args) > 0) {
        _tuple_input<N + 1, Tuple, Args...>(t, sizes...);
      }
    }
    template <int N, class Tuple, __details::is_vec T, class... Args,
              class Size, class... Sizes>
    constexpr auto _tuple_input(Tuple& t, Size size, Sizes... sizes) {
      std::get<N>(t) = _input<T>(size);
      if constexpr (sizeof...(Args) > 0) {
        _tuple_input<N + 1, Tuple, Args...>(t, sizes...);
      }
    }
    template <int N, class Tuple, __details::is_mat T, class... Args,
              class Size, class... Sizes>
    constexpr auto _tuple_input(Tuple& t, Size size_h, Size size_w,
                                Sizes... sizes) {
      std::get<N>(t) = _input<T>(size_h, size_w);
      if constexpr (sizeof...(Args) > 0) {
        _tuple_input<N + 1, Tuple, Args...>(t, sizes...);
      }
    }

    template <class... Args, class... Sizes>
    requires(std::convertible_to<Sizes, size_t>&&...) constexpr auto in(
        Sizes... sizes) {
      auto base = std::tuple<Args...>();
      _tuple_input<0, decltype(base), Args...>(base, sizes...);
      return base;
    }

  }  // namespace io

}  // namespace mtd
#line 6 "Library/Range/istream.hpp"

namespace mtd {
  namespace ranges {

    constexpr int _inf = 1e9;

    template <class... Args>
    struct istream_view
        : public std::ranges::view_interface<istream_view<Args...>> {
      class iterator {
        int count;
        std::tuple<Args...> val;

      public:
        using difference_type = int;
        using value_type = decltype(val);
        using iterator_concept = std::input_iterator_tag;

        constexpr iterator() = default;
        constexpr explicit iterator(int _count) : count(_count) {
          operator++();
        }

        constexpr auto operator*() const { return val; }
        constexpr auto& operator++() {
          --count;
          if (count >= 0) { val = io::in<Args...>(); }
          return *this;
        }
        constexpr auto operator++(int) { return ++*this; }

        constexpr auto operator==(const iterator& s) const {
          return count == s.count;
        }
        constexpr auto operator==(std::default_sentinel_t) const {
          return count < 0 || std::cin.eof() || std::cin.fail() ||
                 std::cin.bad();
        }
        constexpr friend auto operator==(std::default_sentinel_t s,
                                         const iterator& li) {
          return li == s;
        }
      };

      int count;

    public:
      constexpr explicit istream_view(int _count) : count(_count) {}
      constexpr explicit istream_view() : istream_view(_inf) {}
      constexpr auto begin() const { return iterator(count); }
      constexpr auto end() const { return std::default_sentinel; }
    };
  }  // namespace ranges

  namespace views {
    namespace __detail {
      template <typename... _Args>
      concept __can_istream_view = requires {
        ranges::istream_view(std::declval<_Args>()...);
      };
    }  // namespace __detail

    template <class... Args>
    struct _Istream {
      template <class... _Tp>
      requires __detail::__can_istream_view<_Tp...>
      constexpr auto operator() [[nodiscard]] (_Tp&&... __e) const {
        return ranges::istream_view<Args...>(std::forward<_Tp>(__e)...);
      }
    };

    template <class... Args>
    inline constexpr _Istream<Args...> istream{};
  }  // namespace views

}  // namespace mtd

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