ceph/src/boost/boost/hana/fwd/transform.hpp

   1 /*!
   2 @file
   3 Forward declares `boost::hana::transform`.
   4
   5 @copyright Louis Dionne 2013-2017
   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_TRANSFORM_HPP
  11 #define BOOST_HANA_FWD_TRANSFORM_HPP
  12
  13 #include <boost/hana/config.hpp>
  14 #include <boost/hana/core/when.hpp>
  15
  16
  17 BOOST_HANA_NAMESPACE_BEGIN
  18     //! Map a function over a `Functor`.
  19     //! @ingroup group-Functor
  20     //!
  21     //!
  22     //! Signature
  23     //! ---------
  24     //! Given `F` a Functor, the signature is
  25     //! \f$
  26     //!     \mathtt{transform} : F(T) \times (T \to U) \to F(U)
  27     //! \f$
  28     //!
  29     //! @param xs
  30     //! The structure to map `f` over.
  31     //!
  32     //! @param f
  33     //! A function called as `f(x)` on element(s) `x` of the structure,
  34     //! and returning a new value to replace `x` in the structure.
  35     //!
  36     //!
  37     //! Example
  38     //! -------
  39     //! @include example/transform.cpp
  40 #ifdef BOOST_HANA_DOXYGEN_INVOKED
  41     constexpr auto transform = [](auto&& xs, auto&& f) {
  42         return tag-dispatched;
  43     };
  44 #else
  45     template <typename Xs, typename = void>
  46     struct transform_impl : transform_impl<Xs, when<true>> { };
  47
  48     struct transform_t {
  49         template <typename Xs, typename F>
  50         constexpr auto operator()(Xs&& xs, F&& f) const;
  51     };
  52
  53     constexpr transform_t transform{};
  54 #endif
  55 BOOST_HANA_NAMESPACE_END
  56
  57 #endif // !BOOST_HANA_FWD_TRANSFORM_HPP