Alepha/type_lisp.h

static_assert( __cplusplus > 2020'99 );

#pragma once

#include <Alepha/Alepha.h>

#include <type_traits>
#include <tuple>

namespace Alepha::Hydrogen  ::detail::  type_lisp_m
{
	inline namespace exports {}

	namespace exports
	{
		template< typename ... > struct TypeList {};

		using Nil= TypeList<>;

		template< typename T >
		constexpr bool is_nil_v= std::is_same_v< T, Nil >;
	}

	template< typename T >
	constexpr bool is_type_list_v= false;

	template< typename ... Args >
	constexpr bool is_type_list_v< TypeList< Args... > >{ true };

	namespace exports
	{
		template< typename Type >
		concept TypeListType= is_type_list_v< Type >;
	}

	template< typename T >
	struct tuple_from_list;

	namespace exports
	{
		template< typename List >
		using tuple_from_list_t= typename tuple_from_list< List >::type;
	}

	template< typename ... Members >
	struct tuple_from_list< TypeList< Members... > >
	{
		using type= std::tuple< Members... >;
	};

	template< TypeListType >
	struct list_size;

	template< typename ... Members >
	struct list_size< TypeList< Members... > >
	{
		static const std::size_t value= sizeof...( Members );
	};

	namespace exports
	{
		template< TypeListType List >
		constexpr std::size_t list_size_v= list_size< List >::value;
	}

	template< typename List >
	struct car_impl { using type= Nil; };

	template< typename Arg0, typename ... Args >
	struct car_impl< TypeList< Arg0, Args... > >
	{
		using type= Arg0;
	};

	template< typename List >
	struct cdr_impl { using type= Nil; };

	template< typename Arg0, typename ... Args >
	struct cdr_impl< TypeList< Arg0, Args... > >
	{
		using type= TypeList< Args... >;
	};

	namespace exports
	{
		template< typename List >
		using car_t= typename car_impl< List >::type;

		template< typename List >
		using cdr_t= typename cdr_impl< List >::type;
	}

	template< typename List, typename Element >
	struct list_contains
	{
		static const bool value= std::is_same_v< Element, car_t< List > > or list_contains< cdr_t< List >, Element >::value;
	};

	template< typename Element >
	struct list_contains< Nil, Element > : std::false_type {};

	namespace exports
	{
		template< typename List, typename Element >
		constexpr bool list_contains_v= list_contains< List, Element >::value;
	}

	struct Alpha;
	struct Beta;
	struct Gamma;
	static_assert(     list_contains_v< TypeList< Alpha, Beta >, Alpha > );
	static_assert(     list_contains_v< TypeList< Alpha, Beta >, Beta > );
	static_assert( not list_contains_v< TypeList< Alpha, Beta >, Gamma > );

	template< typename Element, typename List >
	struct cons;

	template< typename Element, typename ... Members >
	struct cons< Element, TypeList< Members... > >
	{
		using type= TypeList< Element, Members... >;
	};

	namespace exports
	{
		template< typename Element, typename List >
		using cons_t= typename cons< Element, List >::type;
	}

	template< typename Tuple >
	struct list_from_tuple;

	namespace exports
	{
		template< typename Tuple >
		using list_from_tuple_t= typename list_from_tuple< Tuple >::type;
	}

	template< typename ... Members >
	struct list_from_tuple< std::tuple< Members... > >
	{
		using type= TypeList< Members... >;
	};

	template< typename Left, typename Right >
	struct list_cat;

	namespace exports
	{
		template< typename Left, typename Right >
		using list_cat_t= typename list_cat< Left, Right >::type;
	}

	template< typename ... LeftArgs, typename ... RightArgs >
	struct list_cat< TypeList< LeftArgs... >, TypeList< RightArgs... > >
	{
		using type= TypeList< LeftArgs..., RightArgs... >;
	};

	template< typename Item, std::size_t count >
	struct repeat;

	namespace exports
	{
		template< typename Item, std::size_t count >
		using repeat_t= typename repeat< Item, count >::type;
	}

	template< typename Item, std::size_t count >
	struct repeat
	{
		using type= cons_t< Item, repeat_t< Item, count - 1 > >;
	};

	template< typename Item >
	struct repeat< Item, 0 >
	{
		using type= Nil;
	};


	template< TypeListType list >
	struct strip_last;

	namespace exports
	{
		template< typename list >
		using strip_last_t= tuple_from_list_t< typename strip_last< list_from_tuple_t< list > >::type >;
	}

	template< TypeListType list >
	struct strip_last
	{
		using type= cons_t< car_t< list >, typename strip_last< cdr_t< list > >::type >;
	};

	template< typename last >
	struct strip_last< TypeList< last > >
	{
		using type= Nil;
	};
}

namespace Alepha::Hydrogen::inline exports::inline type_lisp_m
{
	using namespace detail::type_lisp_m::exports;
}