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

   1 /*!
   2 @file
   3 Forward declares `boost::hana::adjust_if`.
   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_ADJUST_IF_HPP
  11 #define BOOST_HANA_FWD_ADJUST_IF_HPP
  12
  13 #include <boost/hana/config.hpp>
  14 #include <boost/hana/core/when.hpp>
  15
  16
  17 BOOST_HANA_NAMESPACE_BEGIN
  18     //! Apply a function on all the elements of a structure satisfying a predicate.
  19     //! @ingroup group-Functor
  20     //!
  21     //! Given a Functor, a predicate `pred` and a function `f`, `adjust_if`
  22     //! will _adjust_ the elements of the Functor that satisfy the predicate
  23     //! with the function `f`. In other words, `adjust_if` will return a new
  24     //! Functor equal to the original one, except that the elements satisfying
  25     //! the predicate will be transformed with the given function. Elements
  26     //! for which the predicate is not satisfied are left untouched, and they
  27     //! are kept as-is in the resulting Functor.
  28     //!
  29     //!
  30     //! Signature
  31     //! ---------
  32     //! Given a `Functor` `F` and a `Logical` `Bool`, the signature is
  33     //! \f$
  34     //!     \mathtt{adjust_if} : F(T) \times (T \to Bool) \times (T \to T) \to F(T)
  35     //! \f$
  36     //!
  37     //! @param xs
  38     //! The structure to adjust with `f`.
  39     //!
  40     //! @param pred
  41     //! A function called as `pred(x)` for each element of the Functor,
  42     //! and returning whether `f` should be applied on that element.
  43     //!
  44     //! @param f
  45     //! A function called as `f(x)` on the element(s) of the Functor that
  46     //! satisfy the predicate.
  47     //!
  48     //!
  49     //! Example
  50     //! -------
  51     //! @include example/adjust_if.cpp
  52 #ifdef BOOST_HANA_DOXYGEN_INVOKED
  53     constexpr auto adjust_if = [](auto&& xs, auto const& pred, auto const& f) {
  54         return tag-dispatched;
  55     };
  56 #else
  57     template <typename Xs, typename = void>
  58     struct adjust_if_impl : adjust_if_impl<Xs, when<true>> { };
  59
  60     struct adjust_if_t {
  61         template <typename Xs, typename Pred, typename F>
  62         constexpr auto operator()(Xs&& xs, Pred const& pred, F const& f) const;
  63     };
  64
  65     constexpr adjust_if_t adjust_if{};
  66 #endif
  67 BOOST_HANA_NAMESPACE_END
  68
  69 #endif // !BOOST_HANA_FWD_ADJUST_IF_HPP