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

   1 /*!
   2 @file
   3 Forward declares `boost::hana::remove`.
   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_REMOVE_HPP
  11 #define BOOST_HANA_FWD_REMOVE_HPP
  12
  13 #include <boost/hana/config.hpp>
  14 #include <boost/hana/core/when.hpp>
  15
  16
  17 BOOST_HANA_NAMESPACE_BEGIN
  18     //! Remove all the elements of a monadic structure that are equal to some
  19     //! value.
  20     //! @ingroup group-MonadPlus
  21     //!
  22     //! Given a monadic structure `xs` and a `value`, `remove` returns a new
  23     //! monadic structure equal to `xs` without all its elements that are
  24     //! equal to the given `value`. `remove` is equivalent to `remove_if`
  25     //! with the `equal.to(value)` predicate, i.e.
  26     //! @code
  27     //!     remove(xs, value) == remove_if(xs, equal.to(value))
  28     //! @endcode
  29     //!
  30     //!
  31     //! Signature
  32     //! ---------
  33     //! Given a MonadPlus `M` and a value of type `T`, the signature is
  34     //! \f$
  35     //!     \mathrm{remove} : M(T) \times T \to M(T)
  36     //! \f$
  37     //!
  38     //! @param xs
  39     //! A monadic structure to remove some elements from.
  40     //!
  41     //! @param value
  42     //! A value that is compared to every element `x` of the structure.
  43     //! Elements of the structure that are equal to that value are removed
  44     //! from the structure. This requires every element to be Comparable
  45     //! with `value`. Furthermore, in the current version of the library,
  46     //! comparing `value` with any element of the structure must yield a
  47     //! compile-time Logical.
  48     //!
  49     //!
  50     //! Example
  51     //! -------
  52     //! @include example/remove.cpp
  53 #ifdef BOOST_HANA_DOXYGEN_INVOKED
  54     constexpr auto remove = [](auto&& xs, auto&& value) {
  55         return tag-dispatched;
  56     };
  57 #else
  58     template <typename M, typename = void>
  59     struct remove_impl : remove_impl<M, when<true>> { };
  60
  61     struct remove_t {
  62         template <typename Xs, typename Value>
  63         constexpr auto operator()(Xs&& xs, Value&& value) const;
  64     };
  65
  66     constexpr remove_t remove{};
  67 #endif
  68 BOOST_HANA_NAMESPACE_END
  69
  70 #endif // !BOOST_HANA_FWD_REMOVE_HPP