hana/fwd/replace_if.hpp

0001 /*!
0002 @file
0003 Forward declares `boost::hana::replace_if`.
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_REPLACE_IF_HPP
0011 #define BOOST_HANA_FWD_REPLACE_IF_HPP
0012
0013 #include <boost/hana/config.hpp>
0014 #include <boost/hana/core/when.hpp>
0015
0016
0017 namespace boost { namespace hana {
0018     //! Replace all the elements of a structure satisfying a `predicate`
0019     //! with a fixed value.
0020     //! @ingroup group-Functor
0021     //!
0022     //!
0023     //! Signature
0024     //! ---------
0025     //! Given `F` a Functor and `Bool` a Logical, the signature is
0026     //! \f$
0027     //!     \mathtt{replace\_if} : F(T) \times (T \to Bool) \times T \to F(T)
0028     //! \f$
0029     //!
0030     //! @param xs
0031     //! The structure to replace elements of.
0032     //!
0033     //! @param predicate
0034     //! A function called as `predicate(x)` for element(s) `x` of the
0035     //! structure and returning a `Logical` representing whether `x`
0036     //! should be replaced by `value`.
0037     //!
0038     //! @param value
0039     //! A value by which every element `x` of the structure for which
0040     //! `predicate` returns a true-valued `Logical` is replaced.
0041     //!
0042     //!
0043     //! Example
0044     //! -------
0045     //! @include example/replace_if.cpp
0046 #ifdef BOOST_HANA_DOXYGEN_INVOKED
0047     constexpr auto replace_if = [](auto&& xs, auto&& predicate, auto&& value) {
0048         return tag-dispatched;
0049     };
0050 #else
0051     template <typename Xs, typename = void>
0052     struct replace_if_impl : replace_if_impl<Xs, when<true>> { };
0053
0054     struct replace_if_t {
0055         template <typename Xs, typename Pred, typename Value>
0056         constexpr auto operator()(Xs&& xs, Pred&& pred, Value&& value) const;
0057     };
0058
0059     BOOST_HANA_INLINE_VARIABLE constexpr replace_if_t replace_if{};
0060 #endif
0061 }} // end namespace boost::hana
0062
0063 #endif // !BOOST_HANA_FWD_REPLACE_IF_HPP