From a90a1a776eae1fdc90c1fbb66cf058f690345c4a Mon Sep 17 00:00:00 2001
From: ADAM David Alan Martin <adam@pyp-e.io>
Date: Wed, 10 Jul 2024 20:28:51 -0400
Subject: [PATCH] Add a `NamedOperator` facility to Alepha.

This permits naming operators via an enhanced enum and then
looking them up.  This is a useful component for quick
scripting language functionalities.
---
 Utility/CMakeLists.txt                    |  1 +
 Utility/NamedOperator.h                   | 64 +++++++++++++++++++++++
 Utility/NamedOperator.test/0.cc           | 31 +++++++++++
 Utility/NamedOperator.test/CMakeLists.txt |  1 +
 4 files changed, 97 insertions(+)
 create mode 100644 Utility/NamedOperator.h
 create mode 100644 Utility/NamedOperator.test/0.cc
 create mode 100644 Utility/NamedOperator.test/CMakeLists.txt

diff --git a/Utility/CMakeLists.txt b/Utility/CMakeLists.txt
index 2c1bf06..6d3634f 100644
--- a/Utility/CMakeLists.txt
+++ b/Utility/CMakeLists.txt
@@ -4,3 +4,4 @@ target_sources( alepha PRIVATE
 
 add_subdirectory( derived_pointer_cast.test )
 add_subdirectory( print_number.test )
+add_subdirectory( NamedOperator.test )
diff --git a/Utility/NamedOperator.h b/Utility/NamedOperator.h
new file mode 100644
index 0000000..5d7f848
--- /dev/null
+++ b/Utility/NamedOperator.h
@@ -0,0 +1,64 @@
+static_assert( __cplusplus > 2023'00 );
+
+#pragma once
+
+#include <Alepha/Alepha.h>
+
+#include <map>
+#include <functional>
+#include <type_traits>
+
+#include <Alepha/Enum.h>
+
+namespace Alepha::Hydrogen::Utility  ::detail::  NamedOperator_m
+{
+	inline namespace exports
+	{
+		using OperatorName= Enum
+		<
+			"add"_value,
+			"sub"_value,
+			"mul"_value,
+			"mod"_value,
+			"idiv"_value
+		>;
+
+	}
+
+	struct comparator
+	{
+		constexpr auto
+		operator () ( const OperatorName &lhs, const OperatorName &rhs ) const
+		{
+			return lhs.get_index() < rhs.get_index();
+		}
+	};
+
+	namespace exports
+	{
+		template< typename Type >
+		auto
+		getOperatorMap()
+		{
+			std::map< OperatorName, std::function< Type ( Type, Type ) >, comparator > rv
+			{
+				{ "add"_value, std::plus<>{} },
+				{ "sub"_value, std::minus<>{} },
+				{ "mul"_value, std::multiplies<>{} },
+				{ "mod"_value, std::modulus<>{} },
+			};
+
+			if constexpr( std::is_integral_v< Type > )
+			{
+				rv[ "idiv"_value ]= std::divides<>{};
+			}
+
+			return rv;
+		};
+	}
+}
+
+namespace Alepha::Hydrogen::Utility::inline exports::inline NamedOperator_m
+{
+	using namespace detail::NamedOperator_m::exports;
+}
diff --git a/Utility/NamedOperator.test/0.cc b/Utility/NamedOperator.test/0.cc
new file mode 100644
index 0000000..5fe2c0c
--- /dev/null
+++ b/Utility/NamedOperator.test/0.cc
@@ -0,0 +1,31 @@
+static_assert( __cplusplus > 2023'00 );
+
+#include "../NamedOperator.h"
+
+#include <Alepha/Testing/test.h>
+#include <Alepha/Testing/TableTest.h>
+
+#include <Alepha/Utility/enroll.h>
+
+static auto init= Alepha::Utility::enroll <=[]
+{
+	using namespace Alepha::Testing::exports;
+	using namespace Alepha::Utility::NamedOperator_m;
+	using namespace Alepha::literals::enum_literals;
+
+	"Does the named operator system have the expected basic functionality?"_test <= TableTest
+	<
+		[]( const int lhs, const OperatorName name, const int rhs )
+		{
+			return getOperatorMap< int >().at( name )( lhs, rhs );
+		}
+	>
+	::Cases
+	{
+		{ "addition", { 1, "add"_value, 1 }, 2 },
+		{ "subtraction", { 1, "sub"_value, 1 }, 0 },
+		{ "multiplication", { 5, "mul"_value, 5 }, 25 },
+		{ "modulus", { 9, "mod"_value, 5 }, 4 },
+		{ "division", { 5, "idiv"_value, 3 }, 1 },
+	};
+};
diff --git a/Utility/NamedOperator.test/CMakeLists.txt b/Utility/NamedOperator.test/CMakeLists.txt
new file mode 100644
index 0000000..b099603
--- /dev/null
+++ b/Utility/NamedOperator.test/CMakeLists.txt
@@ -0,0 +1 @@
+unit_test( 0 )