forked from boostorg/mp11
88 lines
2.2 KiB
C++
88 lines
2.2 KiB
C++
#ifndef BOOST_INTEGER_SEQUENCE_HPP_INCLUDED
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#define BOOST_INTEGER_SEQUENCE_HPP_INCLUDED
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#include <cstddef>
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namespace boost
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{
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// integer_sequence
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template<class T, T... I> struct integer_sequence
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{
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};
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// detail::make_integer_sequence_impl
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namespace detail
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{
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// iseq_if_c
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template<bool C, class T, class E> struct iseq_if_c_impl;
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template<class T, class E> struct iseq_if_c_impl<true, T, E>
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{
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using type = T;
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};
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template<class T, class E> struct iseq_if_c_impl<false, T, E>
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{
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using type = E;
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};
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template<bool C, class T, class E> using iseq_if_c = typename iseq_if_c_impl<C, T, E>::type;
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// iseq_identity
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template<class T> struct iseq_identity
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{
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using type = T;
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};
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template<class S1, class S2> struct append_integer_sequence;
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template<class T, T... I, T... J> struct append_integer_sequence<integer_sequence<T, I...>, integer_sequence<T, J...>>
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{
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using type = integer_sequence< T, I..., ( J + sizeof...(I) )... >;
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};
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template<class T, T N> struct make_integer_sequence_impl;
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template<class T, T N> struct make_integer_sequence_impl_
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{
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private:
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static_assert( N >= 0, "make_integer_sequence<T, N>: N must not be negative" );
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static T const M = N / 2;
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static T const R = N % 2;
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using S1 = typename make_integer_sequence_impl<T, M>::type;
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using S2 = typename append_integer_sequence<S1, S1>::type;
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using S3 = typename make_integer_sequence_impl<T, R>::type;
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using S4 = typename append_integer_sequence<S2, S3>::type;
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public:
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using type = S4;
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};
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template<class T, T N> struct make_integer_sequence_impl: iseq_if_c<N == 0, iseq_identity<integer_sequence<T>>, iseq_if_c<N == 1, iseq_identity<integer_sequence<T, 0>>, make_integer_sequence_impl_<T, N>>>
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{
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};
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} // namespace detail
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// make_integer_sequence
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template<class T, T N> using make_integer_sequence = typename detail::make_integer_sequence_impl<T, N>::type;
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// index_sequence
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template<std::size_t... I> using index_sequence = integer_sequence<std::size_t, I...>;
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// make_index_sequence
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template<std::size_t N> using make_index_sequence = make_integer_sequence<std::size_t, N>;
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// index_sequence_for
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template<class... T> using index_sequence_for = make_integer_sequence<std::size_t, sizeof...(T)>;
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} // namespace boost
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#endif // #ifndef BOOST_INTEGER_SEQUENCE_HPP_INCLUDED
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