enumerate-contrib-tw.h

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/*
 * MIT License
 *
 * Copyright (c) 2018 Tobias Widlund
 *
 * 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 ENUMERATECONTRIBTW_H
#define ENUMERATECONTRIBTW_H
// Original source available at https://github.com/therocode/enumerate
 
#include "tdecl.h"
 
#include <iterator>
#include <utility>
 
namespace kblib {
 
template <typename It>
struct enumerate_iterator {
   It it;
   std::size_t idx;
 
   using nested_reference = typename std::iterator_traits<It>::reference;
 
   using difference_type = std::ptrdiff_t;
   using value_type = std::pair<nested_reference, std::size_t>;
   using pointer = void;
   using reference = value_type;
   using iterator_category = std::input_iterator_tag;
 
   constexpr auto operator*() -> value_type { return {*it, idx}; }
 
   constexpr auto operator++() & -> enumerate_iterator& {
      ++it;
      ++idx;
      return *this;
   }
   constexpr auto operator++(int) -> enumerate_iterator {
      auto tmp = *this;
      ++(*this);
      return tmp;
   }
 
   template <typename OIt>
   constexpr auto operator==(OIt rhs)
       -> decltype(std::declval<It&>() == std::declval<OIt&>()) {
      return it == rhs;
   }
   template <typename OIt>
   constexpr auto operator!=(OIt rhs)
       -> decltype(std::declval<It&>() != std::declval<OIt&>()) {
      return it != rhs;
   }
 
   constexpr friend auto operator==(enumerate_iterator lhs, enumerate_iterator rhs)
       -> bool {
      return lhs.it == rhs.it;
   }
   constexpr friend auto operator!=(enumerate_iterator lhs, enumerate_iterator rhs)
       -> bool {
      return lhs.it != rhs.it;
   }
};
 
template <typename Range, typename = void>
struct enumerate_t;
 
template <typename Range>
struct enumerate_t<Range, void> {
   detail::no_dangle_t<Range> r;
 
   using range_t = typename std::remove_reference_t<Range>;
   using nested_iterator = decltype(r.begin());
   using nested_end_iterator = decltype(r.end());
   using iterator = enumerate_iterator<nested_iterator>;
   using end_iterator = enumerate_iterator<nested_end_iterator>;
 
   using nested_const_iterator = typename range_t::const_iterator;
   using const_iterator = enumerate_iterator<nested_const_iterator>;
 
   constexpr auto begin() const& noexcept(noexcept(r.cbegin())) -> const_iterator {
      return {r.cbegin(), 0};
   }
   constexpr auto begin() & noexcept(noexcept(r.begin())) -> iterator {
      return {r.begin(), 0};
   }
 
   constexpr auto end() const& noexcept(noexcept(r.cend())) -> const_iterator {
      return {r.cend(), -std::size_t{1}};
   }
   constexpr auto end() & noexcept(noexcept(r.end())) -> end_iterator {
      return {r.end(), -std::size_t{1}};
   }
};
 
template <typename It, typename EndIt>
struct enumerate_t {
   using nested_iterator = It;
   using iterator = enumerate_iterator<nested_iterator>;
   using end_iterator = enumerate_iterator<EndIt>;
 
   constexpr auto begin() const& noexcept -> iterator { return {r_begin, 0}; }
 
   constexpr auto end() const& noexcept -> end_iterator {
      return {r_end, -std::size_t{1}};
   }
 
   It r_begin;
   EndIt r_end;
};
 
template <typename Range>
constexpr auto enumerate(Range&& r) -> enumerate_t<Range&&> {
   return {std::forward<Range>(r)};
}
 
template <typename It, typename EIt>
constexpr auto enumerate(It begin, EIt end) -> enumerate_t<It, EIt> {
   return {begin, end};
}
 
} // namespace kblib
 
#endif // ENUMERATECONTRIBTW_H