Add an identity which works with TableTest

Algorithm/identity.h

@@ -0,0 +1,34 @@
+static_assert( __cplusplus > 2020'99 );
+
+#pragma once
+
+#include <Alepha/Alepha.h>
+
+
+namespace Alepha::Hydrogen::Algorithm  ::detail::  identity_m
+{
+	inline namespace exports
+	{
+		/*!
+		 * Specializable identity function.
+		 *
+		 * Sometimes you need an unambiguous overload for `std::identity`.  Because the 
+		 * standard's version is a function object with an unbounded member template
+		 * `operator ()`, this means that deduction contexts cannod deduce which
+		 * type is the range and domain for the identity object passed.  Normally
+		 * this doesn't matter, but some `Alepha` constructs need to inspect functions.
+		 * to that end, one can use `Alepha::Algorithm::identity< T >` for this purpose
+		 *
+		 * @note This functions effectively the same as the original SGI STL's `identity`
+		 * extension, but with C++11's rvalue semantics.  Although we also use a template
+		 * variable to avoid the need to instantiate.
+		 */
+		template< typename T >
+		constexpr auto identity= []( T val ) { return val; };
+	}
+}
+
+namespace Alepha::Hydrogen::Algorithm::inline exports::inline identity_m
+{
+	using namespace detail::identity_m::exports;
+}