Add a bunch of TMP support.

I'm still on the fence about going full `constexpr` functions
for meta-code.  Overall, I think there's potential here.  I'm
not aiming to replicate what `boost::mpl` or `boost::hana` do
though.  This is more of an internal support mechanism for
Alepha code.  As-needed I'll implement things.

Meta/find.h

@@ -0,0 +1,45 @@
+static_assert( __cplusplus > 201700, "C++17 Required" );
+
+#pragma once
+
+#include <Alepha/Alepha.h>
+
+#include <tuple>
+
+#include <Alepha/Meta/list.h>
+#include <Alepha/Meta/functional.h>
+
+namespace Alepha::Hydrogen::Meta
+{
+	inline namespace exports { inline namespace find_algos {} }
+
+	namespace detail::find_algos
+	{
+		inline namespace exports
+		{
+			template< typename Predicate, typename Tuple >
+			struct find_if;
+
+			template< typename Predicate, typename First, typename ... Elements >
+			struct find_if< Predicate, list< First, Elements... > >
+				: std::conditional_t< Meta::call< Predicate, First >::value, std::true_type, find_if< Predicate, list< Elements... > > >::type {};
+
+			template< typename Predicate >
+			struct find_if< Predicate, list<> > : std::false_type {};
+
+			template< typename Predicate, typename List >
+			constexpr bool find_if_v= find_if< Predicate, List >::value;
+		}
+
+		namespace exports
+		{
+			template< typename Key, typename Argument >
+			constexpr bool find_v= find_if_v< Meta::bind1st< std::is_same, Key >, Argument >;
+		}
+	}
+
+	namespace exports::find_algos
+	{
+		using namespace detail::find_algos::exports;
+	}
+}