106 lines
3.4 KiB
C++
106 lines
3.4 KiB
C++
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/*!
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@file
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Defines `boost::hana::detail::array`.
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@copyright Louis Dionne 2013-2016
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Distributed under the Boost Software License, Version 1.0.
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(See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
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*/
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#ifndef BOOST_HANA_DETAIL_ARRAY_HPP
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#define BOOST_HANA_DETAIL_ARRAY_HPP
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#include <boost/hana/config.hpp>
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#include <boost/hana/detail/algorithm.hpp>
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#include <boost/hana/functional/placeholder.hpp>
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#include <cstddef>
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BOOST_HANA_NAMESPACE_BEGIN namespace detail {
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template <typename N>
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constexpr N factorial(N n) {
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N result = 1;
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while (n != 0)
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result *= n--;
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return result;
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}
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//! @ingroup group-details
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//! A minimal `std::array` with better `constexpr` support.
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//!
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//! We also provide some algorithms from the `constexpr/algorithm.hpp`
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//! header as member functions to make them easier to use in constexpr
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//! contexts, since a `constexpr` `array` can't be mutated in place.
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template <typename T, std::size_t Size>
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struct array {
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T elems_[Size > 0 ? Size : 1];
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constexpr T& operator[](std::size_t n)
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{ return elems_[n]; }
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constexpr T const& operator[](std::size_t n) const
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{ return elems_[n]; }
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constexpr std::size_t size() const noexcept
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{ return Size; }
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constexpr T* begin() noexcept { return elems_; }
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constexpr T const* begin() const noexcept { return elems_; }
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constexpr T* end() noexcept { return elems_ + Size; }
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constexpr T const* end() const noexcept { return elems_ + Size; }
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// Algorithms from constexpr/algorithm.hpp
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constexpr array reverse() const {
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array result = *this;
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detail::reverse(result.begin(), result.end());
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return result;
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}
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template <typename BinaryPred>
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constexpr auto permutations(BinaryPred pred) const {
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array<array<T, Size>, detail::factorial(Size)> result{};
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auto out = result.begin();
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array copy = *this;
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do *out++ = copy;
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while (detail::next_permutation(copy.begin(), copy.end(), pred));
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return result;
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}
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constexpr auto permutations() const
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{ return this->permutations(hana::_ < hana::_); }
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template <typename BinaryPred>
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constexpr auto sort(BinaryPred pred) const {
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array result = *this;
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detail::sort(result.begin(), result.end(), pred);
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return result;
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}
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constexpr auto sort() const
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{ return this->sort(hana::_ < hana::_); }
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template <typename U>
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constexpr auto iota(U value) const {
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array result = *this;
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detail::iota(result.begin(), result.end(), value);
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return result;
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}
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};
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template <typename T, std::size_t M, typename U, std::size_t N>
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constexpr bool operator==(array<T, M> a, array<U, N> b)
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{ return M == N && detail::equal(a.begin(), a.end(), b.begin(), b.end()); }
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template <typename T, std::size_t M, typename U, std::size_t N>
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constexpr bool operator<(array<T, M> a, array<U, N> b) {
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return M < N || detail::lexicographical_compare(a.begin(), a.end(), b.begin(), b.end());
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}
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} BOOST_HANA_NAMESPACE_END
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#endif // !BOOST_HANA_DETAIL_ARRAY_HPP
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