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

   1 /*!
   2 @file
   3 Forward declares `boost::hana::fuse`.
   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_FUSE_HPP
  11 #define BOOST_HANA_FWD_FUSE_HPP
  12
  13 #include <boost/hana/config.hpp>
  14
  15
  16 BOOST_HANA_NAMESPACE_BEGIN
  17     //! Transform a function taking multiple arguments into a function that
  18     //! can be called with a compile-time `Foldable`.
  19     //! @ingroup group-Foldable
  20     //!
  21     //!
  22     //! This function is provided for convenience as a different way of
  23     //! calling `unpack`. Specifically, `fuse(f)` is a function such that
  24     //! @code
  25     //!     fuse(f)(foldable) == unpack(foldable, f)
  26     //!                       == f(x...)
  27     //! @endcode
  28     //! where `x...` are the elements in the foldable. This function is
  29     //! useful when one wants to create a function that accepts a foldable
  30     //! which is not known yet.
  31     //!
  32     //! @note
  33     //! This function is not tag-dispatched; customize `unpack` instead.
  34     //!
  35     //!
  36     //! Example
  37     //! -------
  38     //! @include example/fuse.cpp
  39 #ifdef BOOST_HANA_DOXYGEN_INVOKED
  40     constexpr auto fuse = [](auto&& f) {
  41         return [perfect-capture](auto&& xs) -> decltype(auto) {
  42             return unpack(forwarded(xs), forwarded(f));
  43         };
  44     };
  45 #else
  46     struct fuse_t {
  47         template <typename F>
  48         constexpr auto operator()(F&& f) const;
  49     };
  50
  51     constexpr fuse_t fuse{};
  52 #endif
  53 BOOST_HANA_NAMESPACE_END
  54
  55 #endif // !BOOST_HANA_FWD_FUSE_HPP