From 8f9e88a9c5d83ea043be341a2b8663130e85f5eb Mon Sep 17 00:00:00 2001
From: Felix Morgner <felix.morgner@gmail.com>
Date: Thu, 8 Jun 2023 17:34:00 +0200
Subject: concepts: group in namespaces

---
 source/lib/include/newtype/concepts.hpp | 147 ++++++++++++++++++--------------
 1 file changed, 81 insertions(+), 66 deletions(-)

diff --git a/source/lib/include/newtype/concepts.hpp b/source/lib/include/newtype/concepts.hpp
index c9ef951..8f94a42 100644
--- a/source/lib/include/newtype/concepts.hpp
+++ b/source/lib/include/newtype/concepts.hpp
@@ -9,72 +9,87 @@
 namespace nt::concepts
 {
 
-  template<typename SubjectType>
-  concept equality_comparable = requires(SubjectType lhs, SubjectType rhs) {
-    {
-      lhs == rhs
-    } -> std::convertible_to<bool>;
-  };
-
-  template<typename SubjectType>
-  concept nothrow_equality_comparable = requires(SubjectType lhs, SubjectType rhs) {
-    requires equality_comparable<SubjectType>;
-    {
-      lhs == rhs
-    } noexcept;
-  };
-
-  template<typename SubjectType>
-  concept inequality_comparable = requires(SubjectType lhs, SubjectType rhs) {
-    {
-      lhs != rhs
-    } -> std::convertible_to<bool>;
-  };
-
-  template<typename SubjectType>
-  concept nothrow_inequality_comparable = requires(SubjectType lhs, SubjectType rhs) {
-    requires inequality_comparable<SubjectType>;
-    {
-      lhs != rhs
-    } noexcept;
-  };
-
-  template<typename SubjectType, typename CharType, typename StreamTraits>
-  concept input_streamable = requires(SubjectType subject) {
-    {
-      std::declval<std::basic_istream<CharType, StreamTraits> &>() >> subject
-    } -> std::same_as<std::basic_istream<CharType, StreamTraits> &>;
-  };
-
-  template<typename SubjectType, typename CharType, typename StreamTraits>
-  concept nothrow_input_streamable = requires(SubjectType subject) {
-    requires input_streamable<SubjectType, CharType, StreamTraits>;
-    {
-      std::declval<std::basic_istream<CharType, StreamTraits> &>() >> subject
-    } noexcept;
-  };
-
-  template<typename SubjectType, typename CharType, typename StreamTraits>
-  concept output_streamable = requires(SubjectType subject) {
-    {
-      std::declval<std::basic_ostream<CharType, StreamTraits> &>() << subject
-    } -> std::same_as<std::basic_ostream<CharType, StreamTraits> &>;
-  };
-
-  template<typename SubjectType, typename CharType, typename StreamTraits>
-  concept nothrow_output_streamable = requires(SubjectType subject) {
-    requires output_streamable<SubjectType, CharType, StreamTraits>;
-    {
-      std::declval<std::basic_ostream<CharType, StreamTraits> &>() << subject
-    } noexcept;
-  };
-
-  template<typename SubjectType>
-  concept hashable = requires(SubjectType subject) {
-    {
-      std::hash<SubjectType>{}(subject)
-    } -> std::convertible_to<std::size_t>;
-  };
+  inline namespace comparability
+  {
+
+    template<typename SubjectType>
+    concept equality_comparable = requires(SubjectType lhs, SubjectType rhs) {
+      {
+        lhs == rhs
+      } -> std::convertible_to<bool>;
+    };
+
+    template<typename SubjectType>
+    concept nothrow_equality_comparable = requires(SubjectType lhs, SubjectType rhs) {
+      requires equality_comparable<SubjectType>;
+      {
+        lhs == rhs
+      } noexcept;
+    };
+
+    template<typename SubjectType>
+    concept inequality_comparable = requires(SubjectType lhs, SubjectType rhs) {
+      {
+        lhs != rhs
+      } -> std::convertible_to<bool>;
+    };
+
+    template<typename SubjectType>
+    concept nothrow_inequality_comparable = requires(SubjectType lhs, SubjectType rhs) {
+      requires inequality_comparable<SubjectType>;
+      {
+        lhs != rhs
+      } noexcept;
+    };
+
+  }  // namespace comparability
+
+  inline namespace iostreamable
+  {
+
+    template<typename SubjectType, typename CharType, typename StreamTraits>
+    concept input_streamable = requires(SubjectType subject) {
+      {
+        std::declval<std::basic_istream<CharType, StreamTraits> &>() >> subject
+      } -> std::same_as<std::basic_istream<CharType, StreamTraits> &>;
+    };
+
+    template<typename SubjectType, typename CharType, typename StreamTraits>
+    concept nothrow_input_streamable = requires(SubjectType subject) {
+      requires input_streamable<SubjectType, CharType, StreamTraits>;
+      {
+        std::declval<std::basic_istream<CharType, StreamTraits> &>() >> subject
+      } noexcept;
+    };
+
+    template<typename SubjectType, typename CharType, typename StreamTraits>
+    concept output_streamable = requires(SubjectType subject) {
+      {
+        std::declval<std::basic_ostream<CharType, StreamTraits> &>() << subject
+      } -> std::same_as<std::basic_ostream<CharType, StreamTraits> &>;
+    };
+
+    template<typename SubjectType, typename CharType, typename StreamTraits>
+    concept nothrow_output_streamable = requires(SubjectType subject) {
+      requires output_streamable<SubjectType, CharType, StreamTraits>;
+      {
+        std::declval<std::basic_ostream<CharType, StreamTraits> &>() << subject
+      } noexcept;
+    };
+
+  }  // namespace iostreamable
+
+  inline namespace standard_extensions
+  {
+
+    template<typename SubjectType>
+    concept hashable = requires(SubjectType subject) {
+      {
+        std::hash<SubjectType>{}(subject)
+      } -> std::convertible_to<std::size_t>;
+    };
+
+  }
 
 }  // namespace nt::concepts
 
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