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Make build_number_seq with O(logN) instantiations instead of O(N)

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Ion Gaztañaga
2016-11-12 19:07:34 +01:00
parent 0a719901b6
commit 1f3174baa7
1 changed files with 15 additions and 11 deletions
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26
include/boost/container/detail/variadic_templates_tools.hpp
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@@ -136,21 +136,25 @@ typename get_impl<I, tuple<Values...> >::const_type get(const tuple<Values...>&
// in a function call.
////////////////////////////////////////////////////
template<std::size_t ... Indexes>
struct index_tuple{};
template<std::size_t...> struct index_tuple{ typedef index_tuple type; };
template<std::size_t Num, typename Tuple = index_tuple<> >
struct build_number_seq;
template<class S1, class S2> struct concat_index_tuple;
template<std::size_t Num, std::size_t ... Indexes>
struct build_number_seq<Num, index_tuple<Indexes...> >
: build_number_seq<Num - 1, index_tuple<Indexes..., sizeof...(Indexes)> >
template<std::size_t... I1, std::size_t... I2>
struct concat_index_tuple<index_tuple<I1...>, index_tuple<I2...>>
: index_tuple<I1..., (sizeof...(I1)+I2)...>{};
template<std::size_t N> struct build_number_seq;
template<std::size_t N>
struct build_number_seq
: concat_index_tuple<typename build_number_seq<N/2>::type
,typename build_number_seq<N - N/2 >::type
>::type
{};
template<std::size_t ... Indexes>
struct build_number_seq<0, index_tuple<Indexes...> >
{ typedef index_tuple<Indexes...> type; };
template<> struct build_number_seq<0> : index_tuple<>{};
template<> struct build_number_seq<1> : index_tuple<0>{};
}}} //namespace boost { namespace container { namespace container_detail {