text: /*!
  @file
  Forward declares `boost::hana::slice` and `boost::hana::slice_c`.
  
  @copyright Louis Dionne 2013-2016
  Distributed under the Boost Software License, Version 1.0.
  (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
   */
  
  #ifndef BOOST_HANA_FWD_SLICE_HPP
  #define BOOST_HANA_FWD_SLICE_HPP
  
  #include <boost/hana/config.hpp>
  #include <boost/hana/core/when.hpp>
  
  #include <cstddef>
  
  
  BOOST_HANA_NAMESPACE_BEGIN
      //! Extract the elements of a `Sequence` at the given indices.
      //! @ingroup group-Sequence
      //!
      //! Given an arbitrary sequence of `indices`, `slice` returns a new
      //! sequence of the elements of the original sequence that appear at
      //! those indices. In other words,
      //! @code
      //!     slice([x1, ..., xn], [i1, ..., ik]) == [x_i1, ..., x_ik]
      //! @endcode
      //!
      //! The indices do not have to be ordered or contiguous in any particular
      //! way, but they must not be out of the bounds of the sequence. It is
      //! also possible to specify the same index multiple times, in which case
      //! the element at this index will be repeatedly included in the resulting
      //! sequence.
      //!
      //!
      //! @param xs
      //! The sequence from which a subsequence is extracted.
      //!
      //! @param indices
      //! A compile-time `Foldable` containing non-negative `IntegralConstant`s
      //! representing the indices. The indices are 0-based, and they must all
      //! be in bounds of the `xs` sequence. Note that any `Foldable` will
      //! really do (no need for an `Iterable`, for example); the linearization
      //! of the `indices` is used to determine the order of the elements
      //! included in the slice.
      //!
      //!
      //! Example
      //! -------
      //! @include example/slice.cpp
  #ifdef BOOST_HANA_DOXYGEN_INVOKED
      constexpr auto slice = [](auto&& xs, auto&& indices) {
          return tag-dispatched;
      };
  #else
      template <typename S, typename = void>
      struct slice_impl : slice_impl<S, when<true>> { };
  
      struct slice_t {
          template <typename Xs, typename Indices>
          constexpr auto operator()(Xs&& xs, Indices&& indices) const;
      };
  
      constexpr slice_t slice{};
  #endif
  
      //! Shorthand to `slice` a contiguous range of elements.
      //! @ingroup group-Sequence
      //!
      //! `slice_c` is simply a shorthand to slice a contiguous range of
      //! elements. In particular, `slice_c<from, to>(xs)` is equivalent to
      //! `slice(xs, range_c<std::size_t, from, to>)`, which simply slices
      //! all the elements of `xs` contained in the half-open interval
      //! delimited by `[from, to)`. Like for `slice`, the indices used with
      //! `slice_c` are 0-based and they must be in the bounds of the sequence
      //! being sliced.
      //!
      //!
      //! @tparam from
      //! The index of the first element in the slice.
      //!
      //! @tparam to
      //! One-past the index of the last element in the slice. It must hold
      //! that `from <= to`.
      //!
      //!
      //! Example
      //! -------
      //! @include example/slice_c.cpp
  #ifdef BOOST_HANA_DOXYGEN_INVOKED
      template <std::size_t from, std::size_t to>
      constexpr auto slice_c = [](auto&& xs) {
          return hana::slice(forwarded(xs), hana::range_c<std::size_t, from, to>);
      };
  #else
      template <std::size_t from, std::size_t to>
      struct slice_c_t;
  
      template <std::size_t from, std::size_t to>
      constexpr slice_c_t<from, to> slice_c{};
  #endif
  BOOST_HANA_NAMESPACE_END
  
  #endif // !BOOST_HANA_FWD_SLICE_HPP
  