hana/fwd/adjust.hpp

0001 /*!
0002 @file
0003 Forward declares `boost::hana::adjust`.
0004
0005 Copyright Louis Dionne 2013-2022
0006 Distributed under the Boost Software License, Version 1.0.
0007 (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
0008  */
0009
0010 #ifndef BOOST_HANA_FWD_ADJUST_HPP
0011 #define BOOST_HANA_FWD_ADJUST_HPP
0012
0013 #include <boost/hana/config.hpp>
0014 #include <boost/hana/core/when.hpp>
0015
0016
0017 namespace boost { namespace hana {
0018     //! Apply a function on all the elements of a structure that compare
0019     //! equal to some value.
0020     //! @ingroup group-Functor
0021     //!
0022     //!
0023     //! Signature
0024     //! ---------
0025     //! Given `F` a Functor and `U` a type that can be compared with `T`'s,
0026     //! the signature is
0027     //! \f$
0028     //!     \mathtt{adjust} : F(T) \times U \times (T \to T) \to F(T)
0029     //! \f$
0030     //!
0031     //! @param xs
0032     //! The structure to adjust with `f`.
0033     //!
0034     //! @param value
0035     //! An object that is compared with each element `x` of the structure.
0036     //! Elements of the structure that compare equal to `value` are adjusted
0037     //! with the `f` function.
0038     //!
0039     //! @param f
0040     //! A function called as `f(x)` on the element(s) of the structure that
0041     //! compare equal to `value`.
0042     //!
0043     //!
0044     //! Example
0045     //! -------
0046     //! @include example/adjust.cpp
0047 #ifdef BOOST_HANA_DOXYGEN_INVOKED
0048     constexpr auto adjust = [](auto&& xs, auto&& value, auto&& f) {
0049         return tag-dispatched;
0050     };
0051 #else
0052     template <typename Xs, typename = void>
0053     struct adjust_impl : adjust_impl<Xs, when<true>> { };
0054
0055     struct adjust_t {
0056         template <typename Xs, typename Value, typename F>
0057         constexpr auto operator()(Xs&& xs, Value&& value, F&& f) const;
0058     };
0059
0060     BOOST_HANA_INLINE_VARIABLE constexpr adjust_t adjust{};
0061 #endif
0062 }} // end namespace boost::hana
0063
0064 #endif // !BOOST_HANA_FWD_ADJUST_HPP