Conceptualize value_lens member support.

comparisons.h

@@ -77,23 +77,17 @@ namespace Alepha::Hydrogen
 
 		// Value lens support
 
-		template< typename T, typename= void >
-		struct has_value_lens_member : std::false_type {};
-
 		template< typename T >
-		struct has_value_lens_member< T, std::void_t< decltype( std::declval< const T & >().value_lens() ) > > : std::true_type {};
+		concept MemberValueLensed=
+		Comparable< T >
+				and
+		requires( const T &val )
+		{
+			{ val.value_lens() } -> Concepts::Comparable;
+		};
 
-		template< typename T >
-		constexpr bool has_value_lens_member_v= has_value_lens_member< T >::value;
-
-		template
-		<
-			Comparable T,
-			typename= std::enable_if_t< has_value_lens_member_v< T > >,
-			overload< __LINE__ > = nullptr
-		>
 		constexpr decltype( auto )
-		value_lens( T &t )
+		value_lens( const MemberValueLensed auto &t )
 		{
 			return t.value_lens();
 		}