From 23c71c8d279e312ba30057f27b953b82e93eff6d Mon Sep 17 00:00:00 2001
From: ADAM David Alan Martin <adam@recursive.engineer>
Date: Sun, 22 Oct 2023 05:15:43 -0400
Subject: [PATCH] Auto-generation of comparisons as a capability.

---
 IOStreams/IStreamable.test/0.cc |  5 +++--
 auto_comparable.h               | 35 +++++++++++++++++++++++++++++++++
 2 files changed, 38 insertions(+), 2 deletions(-)
 create mode 100644 auto_comparable.h

diff --git a/IOStreams/IStreamable.test/0.cc b/IOStreams/IStreamable.test/0.cc
index 8b4537a..440486a 100644
--- a/IOStreams/IStreamable.test/0.cc
+++ b/IOStreams/IStreamable.test/0.cc
@@ -7,16 +7,17 @@ static_assert( __cplusplus > 2020'00 );
 
 #include <sstream>
 
+#include <Alepha/auto_comparable.h>
+
 namespace
 {
-	template< typename= Alepha::Capabilities< Alepha::IOStreams::IStreamable > >
+	template< typename= Alepha::Capabilities< Alepha::auto_comparable, Alepha::IOStreams::IStreamable > >
 	struct Agg_core
 	{
 		int x;
 		int y;
 		int z;
 
-		friend bool operator == ( const Agg_core &lhs, const Agg_core &rhs )= default;
 		friend std::ostream &
 		operator << ( std::ostream &os, const Agg_core &agg )
 		{
diff --git a/auto_comparable.h b/auto_comparable.h
new file mode 100644
index 0000000..42bc821
--- /dev/null
+++ b/auto_comparable.h
@@ -0,0 +1,35 @@
+static_assert( __cplusplus > 2020'00 );
+
+#pragma once
+
+#include <Alepha/Alepha.h>
+
+#include <Alepha/Capabilities.h>
+#include <Alepha/comparisons.h>
+
+#include <Alepha/Reflection/tuplizeAggregate.h>
+
+namespace Alepha::Hydrogen  ::detail::  auto_comparable_module
+{
+	inline namespace exports
+	{
+		struct auto_comparable : comparable {};
+	}
+
+	template< typename T >
+	concept AutoComparableAggregate=
+		Capability< T, auto_comparable >
+			and
+		Aggregate< T >;
+
+	constexpr decltype( auto )
+	equality_lens( const AutoComparableAggregate auto &item ) noexcept
+	{
+		return detail::comparisons::magma_hook{ Reflection::tuplizeAggregate( item ) };
+	}
+}
+
+namespace Alepha::Hydrogen::inline exports::inline auto_comparable_module
+{
+	using namespace detail::auto_comparable_module::exports;
+}