From b196e2c10ed8823c681623dfd7bc09b0eb3ad1d2 Mon Sep 17 00:00:00 2001
From: Felix Morgner <felix.morgner@gmail.com>
Date: Thu, 2 Jan 2020 22:38:18 +0100
Subject: new_type: implement support for base comparison

---
 include/newtype/new_type.hpp | 62 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 62 insertions(+)

(limited to 'include')

diff --git a/include/newtype/new_type.hpp b/include/newtype/new_type.hpp
index d22732a..b599c45 100644
--- a/include/newtype/new_type.hpp
+++ b/include/newtype/new_type.hpp
@@ -228,6 +228,37 @@ namespace nt
     return lhs.decay() == rhs.decay();
   }
 
+  /**
+   * @brief Compare an instance of a given nt::new_type with an object of its base type
+   *
+   * @throw This comparison operator throws any exception thrown by the base type comparison operator. It it noexcept iff. the base type
+   * comparison operator is noexcept.
+   * @return true iff. the base type comparison operator returns true, false otherwise.
+   */
+  template<typename BaseType, typename TagType, auto DerivationClause>
+  auto constexpr operator==(new_type<BaseType, TagType, DerivationClause> const & lhs,
+                            BaseType const & rhs) noexcept(impl::is_nothrow_equality_comparable_v<BaseType>)
+      -> std::enable_if_t<DerivationClause(nt::EqBase) && impl::is_equality_comparable_v<BaseType>, bool>
+  {
+    return lhs.decay() == rhs;
+  }
+
+  /**
+   * @brief Compare an instance of the base type with an instance of a given nt::new_type
+   *
+   * @throw This comparison operator throws any exception thrown by the base type comparison operator. It it noexcept iff. the base type
+   * comparison operator is noexcept.
+   * @return true iff. the base type comparison operator returns true, false otherwise.
+   */
+  template<typename BaseType, typename TagType, auto DerivationClause>
+  auto constexpr
+  operator==(BaseType const & lhs,
+             new_type<BaseType, TagType, DerivationClause> const & rhs) noexcept(impl::is_nothrow_equality_comparable_v<BaseType>)
+      -> std::enable_if_t<DerivationClause(nt::EqBase) && impl::is_equality_comparable_v<BaseType>, bool>
+  {
+    return lhs == rhs.decay();
+  }
+
   /**
    * @brief Compare two objects for non-equality
    *
@@ -244,6 +275,37 @@ namespace nt
     return lhs.decay() != rhs.decay();
   }
 
+  /**
+   * @brief Compare an instance of a given nt::new_type with an object of its base type
+   *
+   * @throw This comparison operator throws any exception thrown by the base type comparison operator. It it noexcept iff. the base type
+   * comparison operator is noexcept.
+   * @return true iff. the base type comparison operator returns true, false otherwise.
+   */
+  template<typename BaseType, typename TagType, auto DerivationClause>
+  auto constexpr operator!=(new_type<BaseType, TagType, DerivationClause> const & lhs,
+                            BaseType const & rhs) noexcept(impl::is_nothrow_inequality_comparable_v<BaseType>)
+      -> std::enable_if_t<DerivationClause(nt::EqBase) && impl::is_inequality_comparable_v<BaseType>, bool>
+  {
+    return lhs.decay() != rhs;
+  }
+
+  /**
+   * @brief Compare an instance of the base type with an instance of a given nt::new_type
+   *
+   * @throw This comparison operator throws any exception thrown by the base type comparison operator. It it noexcept iff. the base type
+   * comparison operator is noexcept.
+   * @return true iff. the base type comparison operator returns true, false otherwise.
+   */
+  template<typename BaseType, typename TagType, auto DerivationClause>
+  auto constexpr
+  operator!=(BaseType const & lhs,
+             new_type<BaseType, TagType, DerivationClause> const & rhs) noexcept(impl::is_nothrow_inequality_comparable_v<BaseType>)
+      -> std::enable_if_t<DerivationClause(nt::EqBase) && impl::is_inequality_comparable_v<BaseType>, bool>
+  {
+    return lhs != rhs.decay();
+  }
+
   /// @section Relational operators
 
   /**
-- 
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