ah-uni-functional.H

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/*
                          Aleph_w
 
  Data structures & Algorithms
  version 2.0.0b
  https://github.com/lrleon/Aleph-w
 
  This file is part of Aleph-w library
 
  Copyright (c) 2002-2026 Leandro Rabindranath Leon
 
  Permission is hereby granted, free of charge, to any person obtaining a copy
  of this software and associated documentation files (the "Software"), to deal
  in the Software without restriction, including without limitation the rights
  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  copies of the Software, and to permit persons to whom the Software is
  furnished to do so, subject to the following conditions:
 
  The above copyright notice and this permission notice shall be included in all
  copies or substantial portions of the Software.
 
  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  SOFTWARE.
*/
 
 
# ifndef AH_UNI_FUNCTIONAL_H
# define AH_UNI_FUNCTIONAL_H
 
# include <type_traits>
# include <vector>
# include <optional>
# include <functional>
# include <algorithm>
# include <utility>
# include <tuple>
# include <iterator>
 
namespace Aleph
{
  // ============================================================================
  // Type Traits for Container Detection
  // ============================================================================
 
  namespace uni_functional_detail
  {
    // Detect if type has STL-style begin()/end()
    template <typename T, typename = void>
    struct has_stl_iterator : std::false_type
    {};
 
    template <typename T>
    struct has_stl_iterator<T, std::void_t<
                              decltype(std::declval<const T &>().begin()),
                              decltype(std::declval<const T &>().end()),
                              typename T::value_type
                            >> : std::true_type
    {};
 
    // Detect if type has Aleph-style Iterator with has_curr()/get_curr()/next()
    template <typename T, typename = void>
    struct has_aleph_iterator : std::false_type
    {};
 
    template <typename T>
    struct has_aleph_iterator<T, std::void_t<
                                typename T::Iterator,
                                typename T::Item_Type,
                                decltype(std::declval<typename T::Iterator>().has_curr()),
                                decltype(std::declval<typename T::Iterator>().get_curr()),
                                decltype(std::declval<typename T::Iterator>().next())
                              >> : std::true_type
    {};
 
    // Detect if type has reverse iterators (rbegin/rend)
    template <typename T, typename = void>
    struct has_reverse_iterator : std::false_type
    {};
 
    template <typename T>
    struct has_reverse_iterator<T, std::void_t<
                                  decltype(std::declval<const T &>().rbegin()),
                                  decltype(std::declval<const T &>().rend())
                                >> : std::true_type
    {};
 
    // Get value type from container
    template <typename T, typename = void>
    struct container_value_type;
 
    template <typename T>
    struct container_value_type<T, std::enable_if_t<has_stl_iterator<T>::value>>
    {
      using type = typename T::value_type;
    };
 
    template <typename T>
    struct container_value_type<T, std::enable_if_t<
                                  has_aleph_iterator<T>::value and not has_stl_iterator<T>::value>>
    {
      using type = std::decay_t<typename T::Item_Type>;
    };
 
    template <typename T>
    using value_t = typename container_value_type<std::decay_t<T>>::type;
 
    // Check if container is STL-style
    template <typename T>
    constexpr bool is_stl_container_v = has_stl_iterator<std::decay_t<T>>::value;
 
    // Check if container is Aleph-only
    template <typename T>
    constexpr bool is_aleph_only_v =
        has_aleph_iterator<std::decay_t<T>>::value &&
        not has_stl_iterator<std::decay_t<T>>::value;
  } // namespace uni_functional_detail
 
  // ============================================================================
  // Core Functional Operations
  // ============================================================================
 
  template <typename Op, typename Container>
  void uni_for_each(Op && op, const Container & c)
  {
    auto & op_ref = op;
    if constexpr (uni_functional_detail::is_stl_container_v<Container>)
      for (const auto & item: c)
        op_ref(item);
    else
      for (auto it = c.get_it(); it.has_curr(); it.next_ne())
        op_ref(it.get_curr());
  }
 
  template <typename Op, typename Container>
  void uni_for_each_indexed(Op && op, const Container & c)
  {
    auto & op_ref = op;
    size_t i = 0;
    if constexpr (uni_functional_detail::is_stl_container_v<Container>)
      for (const auto & item: c)
        op_ref(i++, item);
    else
      for (auto it = c.get_it(); it.has_curr(); it.next_ne(), ++i)
        op_ref(i, it.get_curr());
  }
 
  template <typename Op, typename Container>
  [[nodiscard]] auto uni_map(Op && op, const Container & c)
  {
    using T = uni_functional_detail::value_t<Container>;
    using R = std::decay_t<decltype(std::forward<Op>(op)(std::declval<T>()))>;
 
    std::vector<R> result;
    auto & op_ref = op;
 
    if constexpr (uni_functional_detail::is_stl_container_v<Container>)
      {
        result.reserve(c.size());
        for (const auto & item: c)
          result.push_back(op_ref(item));
      }
    else
      for (auto it = c.get_it(); it.has_curr(); it.next_ne())
        result.push_back(op_ref(it.get_curr()));
 
    return result;
  }
 
  template <typename Op, typename Container>
  [[nodiscard]] auto uni_mapi(Op && op, const Container & c)
  {
    using T = uni_functional_detail::value_t<Container>;
    using R = std::decay_t<decltype(std::forward<Op>(op)(size_t{}, std::declval<T>()))>;
 
    std::vector<R> result;
    auto & op_ref = op;
    size_t i = 0;
 
    if constexpr (uni_functional_detail::is_stl_container_v<Container>)
      {
        result.reserve(c.size());
        for (const auto & item: c)
          result.push_back(op_ref(i++, item));
      }
    else
      for (auto it = c.get_it(); it.has_curr(); it.next_ne(), ++i)
        result.push_back(op_ref(i, it.get_curr()));
 
    return result;
  }
 
  template <typename Pred, typename Container>
  [[nodiscard]] auto uni_filter(Pred && pred, const Container & c)
  {
    using T = uni_functional_detail::value_t<Container>;
 
    std::vector<T> result;
    auto & pred_ref = pred;
 
    if constexpr (uni_functional_detail::is_stl_container_v<Container>)
      {
        for (const auto & item: c)
          if (pred_ref(item))
            result.push_back(item);
      }
    else
      {
        for (auto it = c.get_it(); it.has_curr(); it.next_ne())
          if (const auto & item = it.get_curr(); pred_ref(item))
            result.push_back(item);
      }
    return result;
  }
 
  template <typename Pred, typename Container>
  [[nodiscard]] auto uni_filteri(Pred && pred, const Container & c)
  {
    using T = uni_functional_detail::value_t<Container>;
 
    std::vector<T> result;
    auto & pred_ref = pred;
    size_t i = 0;
 
    if constexpr (uni_functional_detail::is_stl_container_v<Container>)
      for (const auto & item: c)
        {
          if (pred_ref(i, item))
            result.push_back(item);
          ++i;
        }
    else
      for (auto it = c.get_it(); it.has_curr(); it.next_ne(), ++i)
        if (const auto & item = it.get_curr(); pred_ref(i, item))
          result.push_back(item);
 
    return result;
  }
 
  template <typename T, typename Op, typename Container>
  [[nodiscard]] T uni_foldl(T init, Op && op, const Container & c)
  {
    T acc = std::move(init);
    auto & op_ref = op;
 
    if constexpr (uni_functional_detail::is_stl_container_v<Container>)
      for (const auto & item: c)
        acc = op_ref(std::move(acc), item);
    else
      for (auto it = c.get_it(); it.has_curr(); it.next_ne())
        acc = op_ref(std::move(acc), it.get_curr());
    return acc;
  }
 
  template <typename T, typename Op, typename Container>
  [[nodiscard]] T uni_reduce(T init, Op && op, const Container & c)
  {
    return uni_foldl(std::move(init), std::forward<Op>(op), c);
  }
 
  template <typename T, typename Op, typename Container>
  [[nodiscard]] std::vector<T> uni_scan_left(T init, Op && op, const Container & c)
  {
    std::vector<T> result;
    result.push_back(init);
 
    T acc = std::move(init);
    auto & op_ref = op;
 
    if constexpr (uni_functional_detail::is_stl_container_v<Container>)
      for (const auto & item: c)
        {
          acc = op_ref(std::move(acc), item);
          result.push_back(acc);
        }
    else
      for (auto it = c.get_it(); it.has_curr(); it.next_ne())
        {
          acc = op_ref(std::move(acc), it.get_curr());
          result.push_back(acc);
        }
    return result;
  }
 
  // ============================================================================
  // Predicates
  // ============================================================================
 
  template <typename Pred, typename Container>
  [[nodiscard]] bool uni_all(Pred && pred, const Container & c)
  {
    auto & pred_ref = pred;
    if constexpr (uni_functional_detail::is_stl_container_v<Container>)
      {
        for (const auto & item: c)
          if (not pred_ref(item))
            return false;
      }
    else
      {
        for (auto it = c.get_it(); it.has_curr(); it.next_ne())
          if (not pred_ref(it.get_curr()))
            return false;
      }
    return true;
  }
 
  template <typename Pred, typename Container>
  [[nodiscard]] bool uni_exists(Pred && pred, const Container & c)
  {
    auto & pred_ref = pred;
    if constexpr (uni_functional_detail::is_stl_container_v<Container>)
      {
        for (const auto & item: c)
          if (pred_ref(item))
            return true;
      }
    else
      {
        for (auto it = c.get_it(); it.has_curr(); it.next_ne())
          if (pred_ref(it.get_curr()))
            return true;
      }
    return false;
  }
 
  template <typename Pred, typename Container>
  [[nodiscard]] bool uni_any(Pred && pred, const Container & c)
  {
    return uni_exists(std::forward<Pred>(pred), c);
  }
 
  template <typename Pred, typename Container>
  [[nodiscard]] bool uni_none(Pred && pred, const Container & c)
  {
    return not uni_exists(std::forward<Pred>(pred), c);
  }
 
  // ============================================================================
  // Finding Elements
  // ============================================================================
 
  template <typename Pred, typename Container>
  [[nodiscard]] auto uni_find(Pred && pred, const Container & c)
  {
    using T = uni_functional_detail::value_t<Container>;
 
    auto & pred_ref = pred;
    if constexpr (uni_functional_detail::is_stl_container_v<Container>)
      {
        for (const auto & item: c)
          if (pred_ref(item))
            return std::optional<T>(item);
      }
    else
      {
        for (auto it = c.get_it(); it.has_curr(); it.next_ne())
          if (const auto & item = it.get_curr(); pred_ref(item))
            return std::optional<T>(item);
      }
    return std::optional<T>{};
  }
 
  template <typename Pred, typename Container>
  [[nodiscard]] std::optional<size_t> uni_find_index(Pred && pred, const Container & c)
  {
    auto & pred_ref = pred;
    size_t i = 0;
 
    if constexpr (uni_functional_detail::is_stl_container_v<Container>)
      {
        for (const auto & item: c)
          {
            if (pred_ref(item))
              return i;
            ++i;
          }
      }
    else
      {
        for (auto it = c.get_it(); it.has_curr(); it.next_ne(), ++i)
          if (pred_ref(it.get_curr()))
            return i;
      }
    return std::nullopt;
  }
 
  template <typename Op, typename Container>
  [[nodiscard]] auto uni_find_mapi(Op && op, const Container & c)
  {
    using T = uni_functional_detail::value_t<Container>;
    using OptType = std::decay_t<decltype(std::forward<Op>(op)(size_t{}, std::declval<T>()))>;
 
    auto & op_ref = op;
    size_t i = 0;
 
    if constexpr (uni_functional_detail::is_stl_container_v<Container>)
      {
        for (const auto & item: c)
          if (auto result = op_ref(i++, item))
            return result;
      }
    else
      {
        for (auto it = c.get_it(); it.has_curr(); it.next_ne(), ++i)
          if (auto result = op_ref(i, it.get_curr()))
            return result;
      }
    return OptType{};
  }
 
  template <typename T, typename Container>
  [[nodiscard]] bool uni_mem(const T & target, const Container & c)
  {
    if constexpr (uni_functional_detail::is_stl_container_v<Container>)
      {
        for (const auto & item: c)
          if (item == target)
            return true;
      }
    else
      {
        for (auto it = c.get_it(); it.has_curr(); it.next_ne())
          if (it.get_curr() == target)
            return true;
      }
    return false;
  }
 
  // ============================================================================
  // Counting
  // ============================================================================
 
  template <typename Pred, typename Container>
  [[nodiscard]] size_t uni_count(Pred && pred, const Container & c)
  {
    auto & pred_ref = pred;
    size_t count = 0;
 
    if constexpr (uni_functional_detail::is_stl_container_v<Container>)
      {
        for (const auto & item: c)
          if (pred_ref(item))
            ++count;
      }
    else
      {
        for (auto it = c.get_it(); it.has_curr(); it.next_ne())
          if (pred_ref(it.get_curr()))
            ++count;
      }
    return count;
  }
 
  template <typename Container>
  [[nodiscard]] size_t uni_length(const Container & c)
  {
    if constexpr (uni_functional_detail::is_stl_container_v<Container>)
      {
        return c.size();
      }
    else
      {
        size_t count = 0;
        for (auto it = c.get_it(); it.has_curr(); it.next_ne())
          ++count;
        return count;
      }
  }
 
  // ============================================================================
  // Taking and Dropping
  // ============================================================================
 
  template <typename Container>
  [[nodiscard]] auto uni_take(size_t n, const Container & c)
  {
    using T = uni_functional_detail::value_t<Container>;
 
    std::vector<T> result;
    result.reserve(n);
    size_t count = 0;
 
    if constexpr (uni_functional_detail::is_stl_container_v<Container>)
      {
        for (const auto & item: c)
          {
            if (count >= n) break;
            result.push_back(item);
            ++count;
          }
      }
    else
      {
        for (auto it = c.get_it(); it.has_curr() and count < n; it.next_ne(), ++count)
          result.push_back(it.get_curr());
      }
    return result;
  }
 
  template <typename Container>
  [[nodiscard]] auto uni_drop(size_t n, const Container & c)
  {
    using T = uni_functional_detail::value_t<Container>;
 
    std::vector<T> result;
    size_t count = 0;
 
    if constexpr (uni_functional_detail::is_stl_container_v<Container>)
      {
        for (const auto & item: c)
          {
            if (count >= n)
              result.push_back(item);
            ++count;
          }
      }
    else
      {
        for (auto it = c.get_it(); it.has_curr(); it.next_ne(), ++count)
          if (count >= n)
            result.push_back(it.get_curr());
      }
    return result;
  }
 
  template <typename Pred, typename Container>
  [[nodiscard]] auto uni_take_while(Pred && pred, const Container & c)
  {
    using T = uni_functional_detail::value_t<Container>;
 
    std::vector<T> result;
    auto & pred_ref = pred;
 
    if constexpr (uni_functional_detail::is_stl_container_v<Container>)
      {
        for (const auto & item: c)
          {
            if (not pred_ref(item))
              break;
            result.push_back(item);
          }
      }
    else
      {
        for (auto it = c.get_it(); it.has_curr(); it.next_ne())
          {
            const auto & item = it.get_curr();
            if (not pred_ref(item))
              break;
            result.push_back(item);
          }
      }
    return result;
  }
 
  template <typename Pred, typename Container>
  [[nodiscard]] auto uni_drop_while(Pred && pred, const Container & c)
  {
    using T = uni_functional_detail::value_t<Container>;
 
    std::vector<T> result;
    auto & pred_ref = pred;
    bool dropping = true;
 
    if constexpr (uni_functional_detail::is_stl_container_v<Container>)
      {
        for (const auto & item: c)
          {
            if (dropping and pred_ref(item))
              continue;
            dropping = false;
            result.push_back(item);
          }
      }
    else
      {
        for (auto it = c.get_it(); it.has_curr(); it.next_ne())
          {
            const auto & item = it.get_curr();
            if (dropping and pred_ref(item))
              continue;
            dropping = false;
            result.push_back(item);
          }
      }
    return result;
  }
 
  // ============================================================================
  // Accessing Elements
  // ============================================================================
 
  template <typename Container>
  [[nodiscard]] auto uni_first(const Container & c)
  {
    using T = uni_functional_detail::value_t<Container>;
 
    if constexpr (uni_functional_detail::is_stl_container_v<Container>)
      {
        auto it = c.begin();
        if (it == c.end())
          return std::optional<T>{};
        return std::optional<T>(*it);
      }
    else
      {
        auto it = c.get_it();
        if (not it.has_curr())
          return std::optional<T>{};
        return std::optional<T>(it.get_curr());
      }
  }
 
  template <typename Container>
  [[nodiscard]] auto uni_last(const Container & c)
  {
    using T = uni_functional_detail::value_t<Container>;
 
    std::optional<T> result;
 
    if constexpr (uni_functional_detail::is_stl_container_v<Container>)
      {
        for (const auto & item: c)
          result = item;
      }
    else
      {
        for (auto it = c.get_it(); it.has_curr(); it.next_ne())
          result = it.get_curr();
      }
    return result;
  }
 
  template <typename Container>
  [[nodiscard]] auto uni_nth(size_t n, const Container & c)
  {
    using T = uni_functional_detail::value_t<Container>;
 
    size_t i = 0;
 
    if constexpr (uni_functional_detail::is_stl_container_v<Container>)
      {
        for (const auto & item: c)
          {
            if (i == n)
              return std::optional<T>(item);
            ++i;
          }
      }
    else
      {
        for (auto it = c.get_it(); it.has_curr(); it.next_ne(), ++i)
          if (i == n)
            return std::optional<T>(it.get_curr());
      }
    return std::optional<T>{};
  }
 
  // ============================================================================
  // Min/Max
  // ============================================================================
 
  template <typename Container>
  [[nodiscard]] auto uni_min(const Container & c)
  {
    using T = uni_functional_detail::value_t<Container>;
 
    std::optional<T> result;
 
    if constexpr (uni_functional_detail::is_stl_container_v<Container>)
      {
        auto it = c.begin();
        if (it == c.end())
          return result;
 
        T min_val = *it;
        ++it;
        for (; it != c.end(); ++it)
          if (*it < min_val)
            min_val = *it;
        return std::optional<T>(min_val);
      }
    else
      {
        auto it = c.get_it();
        if (not it.has_curr())
          return result;
 
        T min_val = it.get_curr();
        it.next_ne();
        for (; it.has_curr(); it.next_ne())
          {
            const auto & item = it.get_curr();
            if (item < min_val)
              min_val = item;
          }
        return std::optional<T>(min_val);
      }
  }
 
  template <typename Container>
  [[nodiscard]] auto uni_max(const Container & c)
  {
    using T = uni_functional_detail::value_t<Container>;
 
    std::optional<T> result;
 
    if constexpr (uni_functional_detail::is_stl_container_v<Container>)
      {
        auto it = c.begin();
        if (it == c.end())
          return result;
 
        T max_val = *it;
        ++it;
        for (; it != c.end(); ++it)
          if (*it > max_val)
            max_val = *it;
        return std::optional<T>(max_val);
      }
    else
      {
        auto it = c.get_it();
        if (not it.has_curr())
          return result;
 
        T max_val = it.get_curr();
        it.next_ne();
        for (; it.has_curr(); it.next_ne())
          {
            const auto & item = it.get_curr();
            if (item > max_val)
              max_val = item;
          }
        return std::optional<T>(max_val);
      }
  }
 
  template <typename Container>
  [[nodiscard]] auto uni_min_max(const Container & c)
  {
    using T = uni_functional_detail::value_t<Container>;
    using ResultType = std::optional<std::pair<T, T>>;
 
    if constexpr (uni_functional_detail::is_stl_container_v<Container>)
      {
        auto it = c.begin();
        if (it == c.end())
          return ResultType{};
 
        T min_val = *it;
        T max_val = *it;
        ++it;
 
        for (; it != c.end(); ++it)
          {
            if (*it < min_val) min_val = *it;
            if (*it > max_val) max_val = *it;
          }
        return ResultType(std::make_pair(min_val, max_val));
      }
    else
      {
        auto it = c.get_it();
        if (not it.has_curr())
          return ResultType{};
 
        T min_val = it.get_curr();
        T max_val = min_val;
        it.next_ne();
 
        for (; it.has_curr(); it.next_ne())
          {
            const auto & item = it.get_curr();
            if (item < min_val) min_val = item;
            if (item > max_val) max_val = item;
          }
        return ResultType(std::make_pair(min_val, max_val));
      }
  }
 
  // ============================================================================
  // Sum and Product
  // ============================================================================
 
  template <typename Container>
  [[nodiscard]] auto uni_sum(const Container & c)
  {
    using T = uni_functional_detail::value_t<Container>;
    T sum{};
 
    if constexpr (uni_functional_detail::is_stl_container_v<Container>)
      {
        for (const auto & item: c)
          sum = sum + item;
      }
    else
      {
        for (auto it = c.get_it(); it.has_curr(); it.next_ne())
          sum = sum + it.get_curr();
      }
    return sum;
  }
 
  template <typename Container>
  [[nodiscard]] auto uni_product(const Container & c)
  {
    using T = uni_functional_detail::value_t<Container>;
 
    if constexpr (uni_functional_detail::is_stl_container_v<Container>)
      {
        auto it = c.begin();
        if (it == c.end()) return T{};
 
        T prod = *it;
        ++it;
        for (; it != c.end(); ++it)
          prod = prod * (*it);
        return prod;
      }
    else
      {
        auto it = c.get_it();
        if (not it.has_curr()) return T{};
 
        T prod = it.get_curr();
        it.next_ne();
        for (; it.has_curr(); it.next_ne())
          prod = prod * it.get_curr();
        return prod;
      }
  }
 
  // ============================================================================
  // Partitioning
  // ============================================================================
 
  template <typename Pred, typename Container>
  [[nodiscard]] auto uni_partition(Pred && pred, const Container & c)
  {
    using T = uni_functional_detail::value_t<Container>;
 
    std::vector<T> matching, non_matching;
    auto & pred_ref = pred;
 
    if constexpr (uni_functional_detail::is_stl_container_v<Container>)
      {
        for (const auto & item: c)
          {
            if (pred_ref(item))
              matching.push_back(item);
            else
              non_matching.push_back(item);
          }
      }
    else
      {
        for (auto it = c.get_it(); it.has_curr(); it.next_ne())
          {
            const auto & item = it.get_curr();
            if (pred_ref(item))
              matching.push_back(item);
            else
              non_matching.push_back(item);
          }
      }
    return std::make_pair(std::move(matching), std::move(non_matching));
  }
 
  // ============================================================================
  // Concatenation and Flattening
  // ============================================================================
 
  template <typename Container1, typename Container2>
  [[nodiscard]] auto uni_concat(const Container1 & c1, const Container2 & c2)
  {
    using T = uni_functional_detail::value_t<Container1>;
 
    std::vector<T> result;
 
    if constexpr (uni_functional_detail::is_stl_container_v<Container1>)
      for (const auto & item: c1)
        result.push_back(item);
    else
      for (auto it = c1.get_it(); it.has_curr(); it.next_ne())
        result.push_back(it.get_curr());
 
    if constexpr (uni_functional_detail::is_stl_container_v<Container2>)
      for (const auto & item: c2)
        result.push_back(item);
    else
      for (auto it = c2.get_it(); it.has_curr(); it.next_ne())
        result.push_back(it.get_curr());
 
    return result;
  }
 
  template <typename Container>
  [[nodiscard]] auto uni_flatten(const Container & c)
  {
    using InnerContainer = uni_functional_detail::value_t<Container>;
    using T = uni_functional_detail::value_t<InnerContainer>;
 
    std::vector<T> result;
 
    if constexpr (uni_functional_detail::is_stl_container_v<Container>)
      {
        for (const auto & inner: c)
          {
            if constexpr (uni_functional_detail::is_stl_container_v<InnerContainer>)
              for (const auto & item: inner)
                result.push_back(item);
            else
              for (auto it = inner.get_it(); it.has_curr(); it.next_ne())
                result.push_back(it.get_curr());
          }
      }
    else
      {
        for (auto it = c.get_it(); it.has_curr(); it.next_ne())
          {
            const auto & inner = it.get_curr();
            if constexpr (uni_functional_detail::is_stl_container_v<InnerContainer>)
              for (const auto & item: inner)
                result.push_back(item);
            else
              for (auto it2 = inner.get_it(); it2.has_curr(); it2.next_ne())
                result.push_back(it2.get_curr());
          }
      }
 
    return result;
  }
 
  template <typename Op, typename Container>
  [[nodiscard]] auto uni_flat_map(Op && op, const Container & c)
  {
    using T = uni_functional_detail::value_t<Container>;
    using InnerContainer = std::decay_t<decltype(std::forward<Op>(op)(std::declval<T>()))>;
    using R = uni_functional_detail::value_t<InnerContainer>;
 
    std::vector<R> result;
    auto & op_ref = op;
 
    if constexpr (uni_functional_detail::is_stl_container_v<Container>)
      {
        for (const auto & item: c)
          {
            auto inner = op_ref(item);
            if constexpr (uni_functional_detail::is_stl_container_v<InnerContainer>)
              for (const auto & inner_item: inner)
                result.push_back(inner_item);
            else
              for (auto it = inner.get_it(); it.has_curr(); it.next_ne())
                result.push_back(it.get_curr());
          }
      }
    else
      {
        for (auto it = c.get_it(); it.has_curr(); it.next_ne())
          {
            auto inner = op_ref(it.get_curr());
            if constexpr (uni_functional_detail::is_stl_container_v<InnerContainer>)
              for (const auto & inner_item: inner)
                result.push_back(inner_item);
            else
              for (auto it2 = inner.get_it(); it2.has_curr(); it2.next_ne())
                result.push_back(it2.get_curr());
          }
      }
 
    return result;
  }
 
  // ============================================================================
  // Uniqueness and Grouping
  // ============================================================================
 
  template <typename Container>
  [[nodiscard]] auto uni_distinct(const Container & c)
  {
    using T = uni_functional_detail::value_t<Container>;
 
    std::vector<T> result;
 
    if constexpr (uni_functional_detail::is_stl_container_v<Container>)
      {
        for (const auto & item: c)
          if (std::find(result.begin(), result.end(), item) == result.end())
            result.push_back(item);
      }
    else
      {
        for (auto it = c.get_it(); it.has_curr(); it.next_ne())
          if (const auto & item = it.get_curr(); std::find(result.begin(), result.end(), item) == result.end())
            result.push_back(item);
      }
 
    return result;
  }
 
  template <typename Key, typename Container>
  [[nodiscard]] auto uni_group_by(Key && key, const Container & c)
  {
    using T = uni_functional_detail::value_t<Container>;
    using K = std::decay_t<decltype(std::forward<Key>(key)(std::declval<T>()))>;
 
    std::vector<std::pair<K, std::vector<T>>> result;
    auto & key_ref = key;
 
    if constexpr (uni_functional_detail::is_stl_container_v<Container>)
      {
        for (const auto & item: c)
          {
            auto k = key_ref(item);
            auto it = std::find_if(result.begin(), result.end(),
                                   [&k](const auto & p) { return p.first == k; });
            if (it != result.end())
              it->second.push_back(item);
            else
              result.emplace_back(std::move(k), std::vector<T>{item});
          }
      }
    else
      {
        for (auto it = c.get_it(); it.has_curr(); it.next_ne())
          {
            const auto & item = it.get_curr();
            auto k = key_ref(item);
            auto res_it = std::find_if(result.begin(), result.end(),
                                       [&k](const auto & p) { return p.first == k; });
            if (res_it != result.end())
              res_it->second.push_back(item);
            else
              result.emplace_back(std::move(k), std::vector<T>{item});
          }
      }
 
    return result;
  }
 
  template <typename Container>
  [[nodiscard]] auto uni_tally(const Container & c)
  {
    using T = uni_functional_detail::value_t<Container>;
 
    std::vector<std::pair<T, size_t>> result;
 
    if constexpr (uni_functional_detail::is_stl_container_v<Container>)
      {
        for (const auto & item: c)
          {
            auto it = std::find_if(result.begin(), result.end(),
                                   [&item](const auto & p) { return p.first == item; });
            if (it != result.end())
              ++it->second;
            else
              result.emplace_back(item, 1);
          }
      }
    else
      {
        for (auto it = c.get_it(); it.has_curr(); it.next_ne())
          {
            const auto & item = it.get_curr();
            auto res_it = std::find_if(result.begin(), result.end(),
                                       [&item](const auto & p) { return p.first == item; });
            if (res_it != result.end())
              ++res_it->second;
            else
              result.emplace_back(item, 1);
          }
      }
 
    return result;
  }
 
  // ============================================================================
  // Conversion
  // ============================================================================
 
  template <typename Container>
  [[nodiscard]] auto uni_to_vector(const Container & c)
  {
    using T = uni_functional_detail::value_t<Container>;
 
    std::vector<T> result;
 
    if constexpr (uni_functional_detail::is_stl_container_v<Container>)
      {
        result.reserve(c.size());
        for (const auto & item: c)
          result.push_back(item);
      }
    else
      {
        for (auto it = c.get_it(); it.has_curr(); it.next_ne())
          result.push_back(it.get_curr());
      }
    return result;
  }
 
  // ============================================================================
  // Comparison
  // ============================================================================
 
  template <typename Container1, typename Container2>
  [[nodiscard]] bool uni_equal(const Container1 & c1, const Container2 & c2)
  {
    constexpr bool c1_is_stl = uni_functional_detail::is_stl_container_v<Container1>;
    constexpr bool c2_is_stl = uni_functional_detail::is_stl_container_v<Container2>;
 
    if constexpr (c1_is_stl and c2_is_stl)
      {
        // Both STL: use standard iterators
        auto it1 = c1.begin();
        auto it2 = c2.begin();
        for (; it1 != c1.end() and it2 != c2.end(); ++it1, ++it2)
          if (not (*it1 == *it2))
            return false;
        return it1 == c1.end() and it2 == c2.end();
      }
    else if constexpr (c1_is_stl and not c2_is_stl)
      {
        // c1 STL, c2 Aleph
        auto it1 = c1.begin();
        auto it2 = c2.get_it();
        for (; it1 != c1.end() and it2.has_curr(); ++it1, it2.next_ne())
          if (not (*it1 == it2.get_curr()))
            return false;
        return it1 == c1.end() and not it2.has_curr();
      }
    else if constexpr (not c1_is_stl and c2_is_stl)
      {
        // c1 Aleph, c2 STL
        auto it1 = c1.get_it();
        auto it2 = c2.begin();
        for (; it1.has_curr() and it2 != c2.end(); it1.next_ne(), ++it2)
          if (not (it1.get_curr() == *it2))
            return false;
        return not it1.has_curr() and it2 == c2.end();
      }
    else
      {
        // Both Aleph
        auto it1 = c1.get_it();
        auto it2 = c2.get_it();
        for (; it1.has_curr() and it2.has_curr(); it1.next_ne(), it2.next_ne())
          if (not (it1.get_curr() == it2.get_curr()))
            return false;
        return not it1.has_curr() and not it2.has_curr();
      }
  }
 
  template <typename Container1, typename Container2>
  [[nodiscard]] int uni_compare(const Container1 & c1, const Container2 & c2)
  {
    constexpr bool c1_is_stl = uni_functional_detail::is_stl_container_v<Container1>;
    constexpr bool c2_is_stl = uni_functional_detail::is_stl_container_v<Container2>;
 
    if constexpr (c1_is_stl and c2_is_stl)
      {
        // Both STL: use standard iterators
        auto it1 = c1.begin();
        auto it2 = c2.begin();
        for (; it1 != c1.end() and it2 != c2.end(); ++it1, ++it2)
          {
            if (*it1 < *it2) return -1;
            if (*it2 < *it1) return 1;
          }
        if (it1 == c1.end() and it2 == c2.end()) return 0;
        return (it1 == c1.end()) ? -1 : 1;
      }
    else if constexpr (c1_is_stl and not c2_is_stl)
      {
        // c1 STL, c2 Aleph
        auto it1 = c1.begin();
        auto it2 = c2.get_it();
        for (; it1 != c1.end() and it2.has_curr(); ++it1, it2.next_ne())
          {
            if (*it1 < it2.get_curr()) return -1;
            if (it2.get_curr() < *it1) return 1;
          }
        if (it1 == c1.end() and not it2.has_curr()) return 0;
        return (it1 == c1.end()) ? -1 : 1;
      }
    else if constexpr (not c1_is_stl and c2_is_stl)
      {
        // c1 Aleph, c2 STL
        auto it1 = c1.get_it();
        auto it2 = c2.begin();
        for (; it1.has_curr() and it2 != c2.end(); it1.next_ne(), ++it2)
          {
            if (it1.get_curr() < *it2) return -1;
            if (*it2 < it1.get_curr()) return 1;
          }
        if (not it1.has_curr() and it2 == c2.end()) return 0;
        return (not it1.has_curr()) ? -1 : 1;
      }
    else
      {
        // Both Aleph
        auto it1 = c1.get_it();
        auto it2 = c2.get_it();
        for (; it1.has_curr() and it2.has_curr(); it1.next_ne(), it2.next_ne())
          {
            if (it1.get_curr() < it2.get_curr()) return -1;
            if (it2.get_curr() < it1.get_curr()) return 1;
          }
        if (not it1.has_curr() and not it2.has_curr()) return 0;
        return (not it1.has_curr()) ? -1 : 1;
      }
  }
} // end namespace Aleph
 
# endif // AH_UNI_FUNCTIONAL_H