From b5fb8c76f2dcb5d4965b3dd4eeb2c6b3344125e6 Mon Sep 17 00:00:00 2001
From: ADAM David Alan Martin <adam@pyp-e.io>
Date: Fri, 5 Jul 2024 11:54:01 -0400
Subject: [PATCH] Create C++26(?) emulation of `template for`.

---
 CMakeLists.txt                        |  1 +
 template_for_each.h                   | 27 +++++++++++++++++
 template_for_each.test/0.cc           | 42 +++++++++++++++++++++++++++
 template_for_each.test/CMakeLists.txt |  1 +
 4 files changed, 71 insertions(+)
 create mode 100644 template_for_each.test/0.cc
 create mode 100644 template_for_each.test/CMakeLists.txt

diff --git a/CMakeLists.txt b/CMakeLists.txt
index b9f4118..2a95f4f 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -38,6 +38,7 @@ add_subdirectory( comparisons.test )
 add_subdirectory( Exception.test )
 add_subdirectory( word_wrap.test )
 add_subdirectory( string_algorithms.test )
+add_subdirectory( template_for_each.test )
 add_subdirectory( tuplize_args.test )
 add_subdirectory( Thread.test )
 add_subdirectory( assertion.test )
diff --git a/template_for_each.h b/template_for_each.h
index 1ec5d61..a3a30a7 100644
--- a/template_for_each.h
+++ b/template_for_each.h
@@ -8,6 +8,8 @@ static_assert( __cplusplus > 2020'99 );
 
 #include <Alepha/Concepts.h>
 
+#include <Alepha/Reflection/tuplizeAggregate.h>
+
 namespace Alepha::Hydrogen  ::detail::  template_for_each_m
 {
 	inline namespace exports
@@ -79,6 +81,31 @@ namespace Alepha::Hydrogen  ::detail::  template_for_each_m
 		{
 			return for_each_syntax_adaptor< const Tuple >{ tuple };
 		}
+
+		template< typename Type >
+		concept TemplateLoopable= false
+				or Tuple< Type >
+				or Aggregate< Type >
+				// or Array< T > // Do we need array support?  Does it matter?
+			;
+
+		template< TemplateLoopable Type >
+		[[nodiscard]]
+		constexpr auto
+		template_for( Type &tuple, std::optional< Reflection::aggregate_tuple_t< Type > > &&tupled= {} ) noexcept
+		{
+			tupled= Reflection::tuplizeAggregate( tuple );
+			return tuple_for_each( *tupled );
+		}
+
+		template< TemplateLoopable Type >
+		[[nodiscard]]
+		constexpr auto
+		template_for( const Type &tuple, std::optional< Reflection::aggregate_tuple_t< Type > > &&tupled= {} ) noexcept
+		{
+			tupled= Reflection::tuplizeAggregate( tuple );
+			return tuple_for_each( *tupled );
+		}
 	}
 }
 
diff --git a/template_for_each.test/0.cc b/template_for_each.test/0.cc
new file mode 100644
index 0000000..628f23a
--- /dev/null
+++ b/template_for_each.test/0.cc
@@ -0,0 +1,42 @@
+static_assert( __cplusplus > 2023'00 );
+
+#include "../template_for_each.h"
+
+#include <Alepha/Testing/test.h>
+#include <Alepha/Testing/TableTest.h>
+
+#include <sstream>
+
+#include <Alepha/Utility/enroll.h>
+
+static auto init= Alepha::Utility::enroll <=[]
+{
+	using namespace Alepha::Testing::literals;
+	using namespace Alepha::Testing::exports;
+
+	struct Example
+	{
+		int x;
+		std::string s;
+		int y;
+	};
+
+	"Can one `template_for` each over a simple struct and get the members into a string?"_test <=TableTest
+	<
+		[]( Example ex )
+		{
+			using Alepha::template_for;
+			std::ostringstream oss;
+			template_for( ex ) <=[&]( const auto &element )
+			{
+				oss << element << std::endl;
+			};
+
+			return oss.str();
+		}
+	>
+	::Cases
+	{
+		{ "Simple case", { { 42, "Hello World", 1138 } }, "42\nHello World\n1138\n" },
+	};
+};
diff --git a/template_for_each.test/CMakeLists.txt b/template_for_each.test/CMakeLists.txt
new file mode 100644
index 0000000..b099603
--- /dev/null
+++ b/template_for_each.test/CMakeLists.txt
@@ -0,0 +1 @@
+unit_test( 0 )