ceph/src/boost/libs/hana/include/boost/hana/fwd/cartesian_product.hpp

   1 /*!
   2 @file
   3 Forward declares `boost::hana::cartesian_product`.
   4
   5 @copyright Louis Dionne 2013-2016
   6 Distributed under the Boost Software License, Version 1.0.
   7 (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
   8  */
   9
  10 #ifndef BOOST_HANA_FWD_CARTESIAN_PRODUCT_HPP
  11 #define BOOST_HANA_FWD_CARTESIAN_PRODUCT_HPP
  12
  13 #include <boost/hana/config.hpp>
  14 #include <boost/hana/core/when.hpp>
  15
  16
  17 BOOST_HANA_NAMESPACE_BEGIN
  18     //! Computes the cartesian product of a sequence of sequences.
  19     //! @ingroup group-Sequence
  20     //!
  21     //! Given a sequence of sequences, `cartesian_product` returns a new
  22     //! sequence of sequences containing the cartesian product of the
  23     //! original sequences. For this method to finish, a finite number
  24     //! of finite sequences must be provided.
  25     //!
  26     //! @note
  27     //! All the sequences must have the same tag, and that tag must also match
  28     //! that of the top-level sequence.
  29     //!
  30     //!
  31     //! Signature
  32     //! ---------
  33     //! Given a `Sequence` `S(T)`, the signature is
  34     //! \f[
  35     //!     \mathtt{cartesian\_product} : S(S(T)) \to S(S(T))
  36     //! \f]
  37     //!
  38     //! @param xs
  39     //! A sequence of sequences of which the cartesian product is computed.
  40     //!
  41     //!
  42     //! Example
  43     //! -------
  44     //! @include example/cartesian_product.cpp
  45 #ifdef BOOST_HANA_DOXYGEN_INVOKED
  46     constexpr auto cartesian_product = [](auto&& xs) {
  47         return tag-dispatched;
  48     };
  49 #else
  50     template <typename S, typename = void>
  51     struct cartesian_product_impl : cartesian_product_impl<S, when<true>> { };
  52
  53     struct cartesian_product_t {
  54         template <typename Xs>
  55         constexpr auto operator()(Xs&& xs) const;
  56     };
  57
  58     constexpr cartesian_product_t cartesian_product{};
  59 #endif
  60 BOOST_HANA_NAMESPACE_END
  61
  62 #endif // !BOOST_HANA_FWD_CARTESIAN_PRODUCT_HPP