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

   1 /*!
   2 @file
   3 Forward declares `boost::hana::replicate`.
   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_REPLICATE_HPP
  11 #define BOOST_HANA_FWD_REPLICATE_HPP
  12
  13 #include <boost/hana/config.hpp>
  14 #include <boost/hana/core/when.hpp>
  15
  16
  17 BOOST_HANA_NAMESPACE_BEGIN
  18     //! Create a monadic structure by combining a lifted value with itself
  19     //! `n` times.
  20     //! @ingroup group-MonadPlus
  21     //!
  22     //! Given a value `x`, a non-negative `IntegralConstant` `n` and the tag
  23     //! of a monadic structure `M`, `replicate` creates a new monadic structure
  24     //! which is the result of combining `x` with itself `n` times inside the
  25     //! monadic structure. In other words, `replicate` simply `lift`s `x` into
  26     //! the monadic structure, and then combines that with itself `n` times:
  27     //! @code
  28     //!     replicate<M>(x, n) == cycle(lift<M>(x), n)
  29     //! @endcode
  30     //!
  31     //! If `n` is zero, then the identity of the `concat` operation is returned.
  32     //! In the case of sequences, this corresponds to creating a new sequence
  33     //! holding `n` copies of `x`.
  34     //!
  35     //!
  36     //! Signature
  37     //! ---------
  38     //! Given an `IntegralConstant` `C` and MonadPlus `M`, the signature is
  39     //! @f$ \mathtt{replicate}_M : T \times C \to M(T) @f$.
  40     //!
  41     //! @tparam M
  42     //! The tag of the returned monadic structure. It must be a
  43     //! model of the MonadPlus concept.
  44     //!
  45     //! @param x
  46     //! The value to lift into a monadic structure and then combine with
  47     //! itself.
  48     //!
  49     //! @param n
  50     //! A non-negative `IntegralConstant` representing the number of times to
  51     //! combine `lift<M>(x)` with itself. If `n == 0`, `replicate` returns
  52     //! `empty<M>()`.
  53     //!
  54     //!
  55     //! Example
  56     //! -------
  57     //! @include example/replicate.cpp
  58 #ifdef BOOST_HANA_DOXYGEN_INVOKED
  59     template <typename M>
  60     constexpr auto replicate = [](auto&& x, auto const& n) {
  61         return tag-dispatched;
  62     };
  63 #else
  64     template <typename M, typename = void>
  65     struct replicate_impl : replicate_impl<M, when<true>> { };
  66
  67     template <typename M>
  68     struct replicate_t;
  69
  70     template <typename M>
  71     constexpr replicate_t<M> replicate{};
  72 #endif
  73 BOOST_HANA_NAMESPACE_END
  74
  75 #endif // !BOOST_HANA_FWD_REPLICATE_HPP