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-rw-r--r--compat/meta.hpp43
1 files changed, 24 insertions, 19 deletions
diff --git a/compat/meta.hpp b/compat/meta.hpp
index b02029a7..8682fdc8 100644
--- a/compat/meta.hpp
+++ b/compat/meta.hpp
@@ -7,17 +7,22 @@
* copyright notice and this permission notice appear in all copies.
*/
-#if 0
-
-#include <tuple>
-#include <cstddef>
+#define OTR_META_INST_FAIL(x) \
+ static_assert(sizeof...(x) == ~0ul); \
+ static_assert(sizeof...(x) == 0u)
namespace meta {
namespace detail {
- template<typename x, typename y>
- struct reverse_;
+ template<typename... xs>
+ struct tuple;
+
+ template<typename... xs>
+ struct reverse_
+ {
+ OTR_META_INST_FAIL(xs);
+ };
template<typename x0, typename... xs, template<typename...> class x, typename... ys>
struct reverse_<x<x0, xs...>, x<ys...>>
@@ -31,28 +36,32 @@ namespace detail {
using type = x<ys...>;
};
- template<template<typename...> class inst, typename x>
- struct lift_;
+ template<template<typename...> class inst, typename... xs>
+ struct lift_
+ {
+ OTR_META_INST_FAIL(xs);
+ };
- template<template<typename...> class inst, template<typename...> class x, typename... xs>
- struct lift_<inst, x<xs...>>
+ template<template<typename...> class to, template<typename...> class from, typename... xs>
+ struct lift_<to, from<xs...>>
{
- using type = inst<xs...>;
+ using type = to<xs...>;
};
} // ns detail
template<typename... xs>
-using reverse = typename detail::reverse_<std::tuple<xs...>, std::tuple<>>::type;
+using reverse = typename detail::reverse_<detail::tuple<xs...>, detail::tuple<>>::type;
-template<template<typename...> class inst, class x>
-using lift = typename detail::lift_<inst, x>::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<typename x, typename... xs>
using first = x;
template<typename x, typename... xs>
-using rest = std::tuple<xs...>;
+using rest = detail::tuple<xs...>;
template<typename... xs>
using butlast = reverse<rest<reverse<xs...>>>;
@@ -60,9 +69,5 @@ using butlast = reverse<rest<reverse<xs...>>>;
template<typename... xs>
using last = lift<first, reverse<xs...>>;
-template<std::size_t max>
-using index_sequence = typename detail::index_sequence_<std::size_t, max, std::size_t(0)>::type;
-
} // ns meta
-#endif