From b01d495beb586d8d18ef592d80f593ea1bbe10e2 Mon Sep 17 00:00:00 2001
From: Felix Morgner <felix.morgner@gmail.com>
Date: Fri, 28 Feb 2020 06:46:26 +0100
Subject: new_type: implement rbegin and crbegin

---
 include/newtype/impl/new_type_iterator_types.hpp | 24 +++++++
 include/newtype/impl/type_traits_extensions.hpp  | 90 ++++++++++++++++++++++++
 include/newtype/new_type.hpp                     | 62 +++++++++++++++-
 3 files changed, 175 insertions(+), 1 deletion(-)

(limited to 'include')

diff --git a/include/newtype/impl/new_type_iterator_types.hpp b/include/newtype/impl/new_type_iterator_types.hpp
index 037f08d..2ea8274 100644
--- a/include/newtype/impl/new_type_iterator_types.hpp
+++ b/include/newtype/impl/new_type_iterator_types.hpp
@@ -30,10 +30,34 @@ namespace nt::impl
     using const_iterator = typename T::const_iterator;
   };
 
+  template<typename T, bool = false, typename = std::void_t<>>
+  struct new_type_reverse_iterator
+  {
+  };
+
+  template<typename T>
+  struct new_type_reverse_iterator<T, true, std::void_t<typename T::reverse_iterator>>
+  {
+    using reverse_iterator = typename T::reverse_iterator;
+  };
+
+  template<typename T, bool = false, typename = std::void_t<>>
+  struct new_type_const_reverse_iterator
+  {
+  };
+
+  template<typename T>
+  struct new_type_const_reverse_iterator<T, true, std::void_t<typename T::const_reverse_iterator>>
+  {
+    using const_reverse_iterator = typename T::const_reverse_iterator;
+  };
+
   template<typename T, bool Enabled>
   struct new_type_iterator_types
       : new_type_iterator<T, Enabled>
       , new_type_const_iterator<T, Enabled>
+      , new_type_reverse_iterator<T, Enabled>
+      , new_type_const_reverse_iterator<T, Enabled>
   {
   };
 
diff --git a/include/newtype/impl/type_traits_extensions.hpp b/include/newtype/impl/type_traits_extensions.hpp
index a9bd6af..f7dafef 100644
--- a/include/newtype/impl/type_traits_extensions.hpp
+++ b/include/newtype/impl/type_traits_extensions.hpp
@@ -578,6 +578,96 @@ namespace nt::impl
     auto constexpr has_cbegin_v = has_cbegin<T>::value;
   }  // namespace iterable_cbegin
 
+  inline namespace iterable_rbegin
+  {
+    template<typename T, typename = void>
+    struct has_free_rbegin : std::false_type
+    {
+    };
+
+    template<typename T>
+    struct has_free_rbegin<T, std::void_t<decltype(rbegin(std::declval<T &>()))>>
+        : std::is_same<typename T::reverse_iterator, std::remove_cvref_t<decltype(begin(std::declval<T &>()))>>
+    {
+    };
+
+    template<typename T>
+    struct has_free_rbegin<T const, std::void_t<decltype(rbegin(std::declval<T const &>()))>>
+        : std::is_same<typename T::const_reverse_iterator, std::remove_cvref_t<decltype(rbegin(std::declval<T const &>()))>>
+    {
+    };
+
+    template<typename T>
+    auto constexpr has_free_rbegin_v = has_free_rbegin<T>::value;
+
+    template<typename T, typename = void>
+    struct has_member_rbegin : std::false_type
+    {
+    };
+
+    template<typename T>
+    struct has_member_rbegin<T, std::void_t<decltype(std::declval<T &>().rbegin())>>
+        : std::is_same<typename T::reverse_iterator, std::remove_cvref_t<decltype(std::declval<T &>().rbegin())>>
+    {
+    };
+
+    template<typename T>
+    struct has_member_rbegin<T const, std::void_t<decltype(std::declval<T const &>().rbegin())>>
+        : std::is_same<typename T::const_reverse_iterator, std::remove_cvref_t<decltype(std::declval<T const &>().rbegin())>>
+    {
+    };
+
+    template<typename T>
+    auto constexpr has_member_rbegin_v = has_member_rbegin<T>::value;
+
+    template<typename T>
+    struct has_rbegin : std::disjunction<has_free_rbegin<T>, has_member_rbegin<T>>
+    {
+    };
+
+    template<typename T>
+    auto constexpr has_rbegin_v = has_rbegin<T>::value;
+  }  // namespace iterable_rbegin
+
+  inline namespace iterable_rbegin
+  {
+    template<typename T, typename = void>
+    struct has_free_crbegin : std::false_type
+    {
+    };
+
+    template<typename T>
+    struct has_free_crbegin<T, std::void_t<decltype(crbegin(std::declval<T const &>()))>>
+        : std::is_same<typename T::const_reverse_iterator, std::remove_cvref_t<decltype(crbegin(std::declval<T const &>()))>>
+    {
+    };
+
+    template<typename T>
+    auto constexpr has_free_crbegin_v = has_free_crbegin<T>::value;
+
+    template<typename T, typename = void>
+    struct has_member_crbegin : std::false_type
+    {
+    };
+
+    template<typename T>
+    struct has_member_crbegin<T, std::void_t<decltype(std::declval<T const &>().crbegin())>>
+        : std::is_same<typename T::const_reverse_iterator, std::remove_cvref_t<decltype(std::declval<T const &>().crbegin())>>
+    {
+    };
+
+    template<typename T>
+    auto constexpr has_member_crbegin_v = has_member_crbegin<T>::value;
+
+    template<typename T>
+    struct has_crbegin : std::disjunction<has_free_crbegin<T>, has_member_crbegin<T>>
+    {
+    };
+
+    template<typename T>
+    auto constexpr has_crbegin_v = has_crbegin<T>::value;
+  }  // namespace iterable_rbegin
+
 }  // namespace nt::impl
 
 #endif
\ No newline at end of file
diff --git a/include/newtype/new_type.hpp b/include/newtype/new_type.hpp
index 24ac71a..36a3927 100644
--- a/include/newtype/new_type.hpp
+++ b/include/newtype/new_type.hpp
@@ -65,7 +65,7 @@ namespace nt
 
     template<typename BaseTypeT, typename TagTypeT, auto DerivationClauseV>
     auto constexpr friend begin(new_type<BaseTypeT, TagTypeT, DerivationClauseV> const & obj)
-        -> std::enable_if_t<DerivationClauseV(nt::Iterable) && impl::has_free_begin_v<BaseTypeT>,
+        -> std::enable_if_t<DerivationClauseV(nt::Iterable) && impl::has_free_begin_v<BaseTypeT const>,
                             typename new_type<BaseTypeT, TagTypeT, DerivationClauseV>::const_iterator>;
 
     template<typename BaseTypeT, typename TagTypeT, auto DerivationClauseV>
@@ -73,6 +73,21 @@ namespace nt
         -> std::enable_if_t<DerivationClauseV(nt::Iterable) && impl::has_free_cbegin_v<BaseTypeT const>,
                             typename new_type<BaseTypeT, TagTypeT, DerivationClauseV>::const_iterator>;
 
+    template<typename BaseTypeT, typename TagTypeT, auto DerivationClauseV>
+    auto constexpr friend rbegin(new_type<BaseTypeT, TagTypeT, DerivationClauseV> & obj)
+        -> std::enable_if_t<DerivationClauseV(nt::Iterable) && impl::has_free_rbegin_v<BaseTypeT>,
+                            typename new_type<BaseTypeT, TagTypeT, DerivationClauseV>::reverse_iterator>;
+
+    template<typename BaseTypeT, typename TagTypeT, auto DerivationClauseV>
+    auto constexpr friend rbegin(new_type<BaseTypeT, TagTypeT, DerivationClauseV> const & obj)
+        -> std::enable_if_t<DerivationClauseV(nt::Iterable) && impl::has_free_rbegin_v<BaseTypeT const>,
+                            typename new_type<BaseTypeT, TagTypeT, DerivationClauseV>::const_reverse_iterator>;
+
+    template<typename BaseTypeT, typename TagTypeT, auto DerivationClauseV>
+    auto constexpr friend crbegin(new_type<BaseTypeT, TagTypeT, DerivationClauseV> const & obj)
+        -> std::enable_if_t<DerivationClauseV(nt::Iterable) && impl::has_free_crbegin_v<BaseTypeT const>,
+                            typename new_type<BaseTypeT, TagTypeT, DerivationClauseV>::const_reverse_iterator>;
+
     using super = impl::new_type_move_assignment<BaseType, TagType>;
 
   public:
@@ -140,6 +155,27 @@ namespace nt
     {
       return this->m_value.cbegin();
     }
+
+    template<typename NewType = new_type, std::enable_if_t<NewType::derivation_clause(nt::Iterable)> * = nullptr>
+    auto constexpr rbegin()
+        -> std::enable_if_t<NewType::derivation_clause(nt::Iterable) && impl::has_member_rbegin_v<BaseType>, typename NewType::reverse_iterator>
+    {
+      return this->m_value.rbegin();
+    }
+
+    template<typename NewType = new_type>
+    auto constexpr rbegin() const -> std::enable_if_t<NewType::derivation_clause(nt::Iterable) && impl::has_member_rbegin_v<BaseType const>,
+                                                      typename NewType::const_reverse_iterator>
+    {
+      return this->m_value.rbegin();
+    }
+
+    template<typename NewType = new_type>
+    auto constexpr crbegin() const -> std::enable_if_t<NewType::derivation_clause(nt::Iterable) && impl::has_member_crbegin_v<BaseType const>,
+                                                       typename NewType::const_reverse_iterator>
+    {
+      return this->m_value.crbegin();
+    }
   };
 
   template<typename BaseType, typename TagType, auto DerivationClause>
@@ -350,6 +386,30 @@ namespace nt
     return cbegin(obj.m_value);
   }
 
+  template<typename BaseType, typename TagType, auto DerivationClause>
+  auto constexpr rbegin(new_type<BaseType, TagType, DerivationClause> & obj)
+      -> std::enable_if_t<DerivationClause(nt::Iterable) && impl::has_free_rbegin_v<BaseType>,
+                          typename new_type<BaseType, TagType, DerivationClause>::reverse_iterator>
+  {
+    return rbegin(obj.m_value);
+  }
+
+  template<typename BaseType, typename TagType, auto DerivationClause>
+  auto constexpr rbegin(new_type<BaseType, TagType, DerivationClause> const & obj)
+      -> std::enable_if_t<DerivationClause(nt::Iterable) && impl::has_free_rbegin_v<BaseType const>,
+                          typename new_type<BaseType, TagType, DerivationClause>::const_reverse_iterator>
+  {
+    return rbegin(obj.m_value);
+  }
+
+  template<typename BaseType, typename TagType, auto DerivationClause>
+  auto constexpr crbegin(new_type<BaseType, TagType, DerivationClause> const & obj)
+      -> std::enable_if_t<DerivationClause(nt::Iterable) && impl::has_free_crbegin_v<BaseType const>,
+                          typename new_type<BaseType, TagType, DerivationClause>::const_reverse_iterator>
+  {
+    return crbegin(obj.m_value);
+  }
+
 }  // namespace nt
 
 namespace std
-- 
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