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

   1 /*!
   2 @file
   3 Forward declares `boost::hana::for_each`.
   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_FOR_EACH_HPP
  11 #define BOOST_HANA_FWD_FOR_EACH_HPP
  12
  13 #include <boost/hana/config.hpp>
  14 #include <boost/hana/core/when.hpp>
  15
  16
  17 BOOST_HANA_NAMESPACE_BEGIN
  18     //! Perform an action on each element of a foldable, discarding
  19     //! the result each time.
  20     //! @ingroup group-Foldable
  21     //!
  22     //! Iteration is done from left to right, i.e. in the same order as when
  23     //! using `fold_left`. If the structure is not finite, this method will
  24     //! not terminate.
  25     //!
  26     //!
  27     //! @param xs
  28     //! The structure to iterate over.
  29     //!
  30     //! @param f
  31     //! A function called as `f(x)` for each element `x` of the structure.
  32     //! The result of `f(x)`, whatever it is, is ignored.
  33     //!
  34     //!
  35     //! Example
  36     //! -------
  37     //! @include example/for_each.cpp
  38 #ifdef BOOST_HANA_DOXYGEN_INVOKED
  39     constexpr auto for_each = [](auto&& xs, auto&& f) -> void {
  40         tag-dispatched;
  41     };
  42 #else
  43     template <typename T, typename = void>
  44     struct for_each_impl : for_each_impl<T, when<true>> { };
  45
  46     struct for_each_t {
  47         template <typename Xs, typename F>
  48         constexpr void operator()(Xs&& xs, F&& f) const;
  49     };
  50
  51     constexpr for_each_t for_each{};
  52 #endif
  53 BOOST_HANA_NAMESPACE_END
  54
  55 #endif // !BOOST_HANA_FWD_FOR_EACH_HPP