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-rw-r--r--compat/meta.hpp53
1 files changed, 53 insertions, 0 deletions
diff --git a/compat/meta.hpp b/compat/meta.hpp
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+++ b/compat/meta.hpp
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+#pragma once
+
+#include <tuple>
+
+namespace meta {
+
+namespace detail {
+
+ template<typename x, typename y>
+ 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 inst, typename x>
+ struct lift_;
+
+ template<template<typename...> class inst, template<typename...> class x, typename... xs>
+ struct lift_<inst, x<xs...>>
+ {
+ using type = inst<xs...>;
+ };
+}
+
+
+template<typename... xs>
+using reverse = typename detail::reverse_<std::tuple<xs...>, std::tuple<>>::type;
+
+template<template<typename...> class inst, class x>
+using lift = typename detail::lift_<inst, x>::type;
+
+template<typename x, typename... xs>
+using first = x;
+
+template<typename x, typename... xs>
+using rest = std::tuple<xs...>;
+
+template<typename... xs>
+using butlast = reverse<rest<reverse<xs...>>>;
+
+template<typename... xs>
+using last = lift<first, reverse<xs...>>;
+
+}