deps/boost_1_63_0/boost/hana/fwd/replace.hpp

   1 /*!
   2 @file
   3 Forward declares `boost::hana::replace`.
   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_REPLACE_HPP
  11 #define BOOST_HANA_FWD_REPLACE_HPP
  12
  13 #include <boost/hana/config.hpp>
  14 #include <boost/hana/core/when.hpp>
  15
  16
  17 BOOST_HANA_NAMESPACE_BEGIN
  18     //! Replace all the elements of a structure that compare equal
  19     //! to some `value` with some new fixed value.
  20     //! @ingroup group-Functor
  21     //!
  22     //!
  23     //! Signature
  24     //! ---------
  25     //! Given `F` a Functor and `U` a type that can be compared with `T`,
  26     //! the signature is
  27     //! \f$
  28     //!     \mathtt{replace} : F(T) \times U \times T \to F(T)
  29     //! \f$
  30     //!
  31     //! @param xs
  32     //! The structure to replace elements of.
  33     //!
  34     //! @param oldval
  35     //! An object compared with each element of the structure. Elements
  36     //! of the structure that compare equal to `oldval` are replaced
  37     //! by `newval` in the new structure.
  38     //!
  39     //! @param newval
  40     //! A value by which every element `x` of the structure that compares
  41     //! equal to `oldval` is replaced.
  42     //!
  43     //!
  44     //! Example
  45     //! -------
  46     //! @include example/replace.cpp
  47 #ifdef BOOST_HANA_DOXYGEN_INVOKED
  48     constexpr auto replace = [](auto&& xs, auto&& oldval, auto&& newval) {
  49         return tag-dispatched;
  50     };
  51 #else
  52     template <typename Xs, typename = void>
  53     struct replace_impl : replace_impl<Xs, when<true>> { };
  54
  55     struct replace_t {
  56         template <typename Xs, typename OldVal, typename NewVal>
  57         constexpr auto operator()(Xs&& xs, OldVal&& oldval, NewVal&& newval) const;
  58     };
  59
  60     constexpr replace_t replace{};
  61 #endif
  62 BOOST_HANA_NAMESPACE_END
  63
  64 #endif // !BOOST_HANA_FWD_REPLACE_HPP