1 files changed, 123 insertions, 0 deletions
diff --git a/compat/meta.hpp b/compat/meta.hpp
new file mode 100644
index 00000000..49686996
--- /dev/null
+++ b/compat/meta.hpp
@@ -0,0 +1,123 @@
+#pragma once
+
+/* Copyright (c) 2017 Stanislaw Halik
+ *
+ * Permission to use, copy, modify, and/or distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ */
+
+namespace meta::detail {
+
+    template<typename... xs>
+    struct tuple;
+
+    template<typename... xs>
+    struct reverse_;
+
+    template<typename x0, typename... xs, template<typename...> class x, typename... ys>
+    struct reverse_<x<x0, xs...>, x<ys...>>
+    {
+        using type = typename reverse_<x<xs...>, x<x0, ys...>>::type;
+    };
+
+    template<template<typename...> class x, typename... ys>
+    struct reverse_<x<>, x<ys...>>
+    {
+        using type = x<ys...>;
+    };
+
+    template<template<typename...> class, typename, typename...> struct lift_;
+
+    template<template<typename...> class to, template<typename...> class from, typename... xs>
+    struct lift_<to, from<xs...>>
+    {
+        using type = to<xs...>;
+    };
+
+    template<typename> struct append_helper;
+
+    template<typename, typename> struct cons_;
+
+    template<typename x, template<typename...> class t, typename... xs>
+    struct cons_<x, t<xs...>>
+    {
+        using type = t<x, xs...>;
+    };
+
+    template<typename> struct append2;
+
+    template<template<typename...> class t, typename... xs>
+    struct append2<t<xs...>>
+    {
+        template<typename> struct append1;
+
+        template<template<typename...> class u, typename... ys>
+        struct append1<u<ys...>>
+        {
+            using type = t<xs..., ys...>;
+        };
+    };
+
+    template<typename, typename...> struct list__;
+
+    template<typename rest, typename... first>
+    struct list__
+    {
+        template<typename> struct list1;
+
+        template<template<typename...> class t, typename... xs>
+        struct list1<t<xs...>>
+        {
+            using type = t<first..., xs...>;
+        };
+
+        using type = typename list1<rest>::type;
+    };
+
+    template<typename xs, typename ys>
+    struct append_
+    {
+        using t1 = append2<xs>;
+        using type = typename t1::template append1<ys>::type;
+    };
+
+} // ns meta::detail
+
+namespace meta {
+    template<typename... xs>
+    using tuple_ = detail::tuple<xs...>;
+
+    template<typename... xs>
+    using reverse = typename detail::reverse_<detail::tuple<xs...>, detail::tuple<>>::type;
+
+    // the to/from order is awkward but mimics function composition
+    template<template<typename...> class to, typename from>
+    using lift = typename detail::lift_<to, from>::type;
+
+    template<template<typename...> class to, typename from>
+    constexpr inline auto lift_v = detail::lift_<to, from>::type::value;
+
+    template<typename x, typename... xs>
+    using first = x;
+
+    template<typename x, typename... xs>
+    using rest = detail::tuple<xs...>;
+
+    template<typename... xs>
+    using butlast = reverse<rest<reverse<xs...>>>;
+
+    template<typename... xs>
+    using last = lift<first, reverse<xs...>>;
+
+    template<typename x, typename rest>
+    using cons = typename detail::cons_<x, rest>::type;
+
+    template<typename xs, typename ys>
+    using append = typename detail::append_<xs, ys>;
+
+    template<typename rest, typename... xs>
+    using list_ = typename detail::list__<rest, xs...>;
+
+} // ns meta
+