made enumerator_iterator_t compatible with raw pointer iterators

include/ranges/enumerate.hpp

@@ -1,66 +1,101 @@
 #pragma once
 #include "types.hpp"
+#include <cstddef>
 #include <ranges>
-
+#include <xutility>
 
 namespace util {
 namespace rg = std::ranges;
 
-template <rg::range R> struct enumerate_iterator_t : rg::iterator_t<R> {
+template <rg::range R> struct enumerate_iterator_t {
   using base = rg::iterator_t<R>;
   using enumerator_type = std::size_t;
   using value_type = std::pair<enumerator_type, rg::range_value_t<R>>;
+  using difference_type = std::ptrdiff_t;
   using reference =
       std::pair<enumerator_type, std::remove_cv_t<rg::range_reference_t<R>>>;
 
+  base base_iter{};
   enumerator_type enumerator{};
 
   enumerate_iterator_t() = default;
-  enumerate_iterator_t(const base &b) : base{b}, enumerator(0) {}
+  enumerate_iterator_t(const base &b) : base_iter{b}, enumerator(0) {}
+  enumerate_iterator_t(base &&b) : base_iter{std::move(b)}, enumerator(0) {}
 
-  auto operator<=>(const enumerate_iterator_t &other) const {
-    return static_cast<const base &>(*this) <=>
-           static_cast<const base &>(other);
+  auto constexpr operator==(const enumerate_iterator_t &other) const -> bool {
+    return base_iter == other.base_iter;
+  }
+
+  template <std::sentinel_for<base> S>
+  auto constexpr operator==(const S &sentinel) const -> bool {
+    return sentinel == base_iter;
+  }
+
+  auto constexpr operator<=>(const enumerate_iterator_t &other) const {
+    return base_iter <=> other.base_iter;
   }
 
   auto inc_enumerator() -> void { enumerator++; }
+  auto dec_enumerator() -> void { enumerator--; }
+  auto dec_enumerator(const difference_type &n) -> void { enumerator -= n; }
 
   auto operator++(int) -> enumerate_iterator_t {
-    const auto result = static_cast<base &>(*this)++;
+    const auto result = *this;
+    base_iter++;
     inc_enumerator();
     return result;
   }
 
   auto operator++() -> enumerate_iterator_t & {
     inc_enumerator();
-    ++static_cast<base &>(*this);
+    ++base_iter;
     return (*this);
   }
 
-  auto operator*() -> reference {
-    return reference(enumerator, *static_cast<base &>(*this));
+  auto operator--(int) -> enumerate_iterator_t
+      requires(std::bidirectional_iterator<base>) {
+    const auto result = *this;
+    base_iter--;
+    dec_enumerator();
+    return result;
   }
+
+  auto operator--()
+      -> enumerate_iterator_t &requires(std::bidirectional_iterator<base>) {
+    dec_enumerator();
+    --base_iter;
+    return (*this);
+  }
+
+  auto constexpr operator+(const difference_type &n) const
+      -> enumerate_iterator_t {
+    auto ret = *this;
+    ret.inc_enumerator(n);
+    base_iter += n;
+
+    return ret;
+  }
+
+  auto operator*() -> reference { return reference(enumerator, *base_iter); }
   auto operator*() const -> reference {
-    return reference(enumerator, *static_cast<const base &>(*this));
+    return reference(enumerator, *base_iter);
   }
 };
 
 template <rg::range R>
 class enumerate_view : public rg::view_interface<enumerate_view<R>> {
-  R base_{};
   isize enumerator{};
-  enumerate_iterator_t<R> iter_{std::begin(base_)};
+  enumerate_iterator_t<R> iter_;
+  enumerate_iterator_t<R> end_;
 
 public:
   enumerate_view() = default;
 
-  constexpr enumerate_view(R base) : base_(base), iter_(std::begin(base_)) {}
-
-  constexpr R base() const & { return base_; }
-  constexpr R base() && { return std::move(base_); }
+  constexpr enumerate_view(R base)
+      : iter_(std::begin(base)), end_(std::end(base)) {}
 
   constexpr auto begin() const { return iter_; }
-  constexpr auto end() const { return std::end(base_); }
+  constexpr auto end() const { return end_; }
 };
 
 namespace detail {