hana/fwd/fold.hpp

0001 /*!
0002 @file
0003 Forward declares `boost::hana::fold`.
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_FOLD_HPP
0011 #define BOOST_HANA_FWD_FOLD_HPP
0012
0013 #include <boost/hana/config.hpp>
0014 #include <boost/hana/fwd/fold_left.hpp>
0015
0016
0017 namespace boost { namespace hana {
0018     //! Equivalent to `fold_left`; provided for convenience.
0019     //! @ingroup group-Foldable
0020     //!
0021     //! `fold` is equivalent to `fold_left`. However, it is not tag-dispatched
0022     //! on its own because it is just an alias to `fold_left`. Also note that
0023     //! `fold` can be called with or without an initial state, just like
0024     //! `fold_left`:
0025     //!
0026     //! @code
0027     //!     fold(xs, state, f) == fold_left(xs, state, f)
0028     //!     fold(xs, f) == fold_left(xs, f)
0029     //! @endcode
0030     //!
0031     //!
0032     //! Example
0033     //! -------
0034     //! @include example/fold.cpp
0035     BOOST_HANA_INLINE_VARIABLE constexpr auto fold = fold_left;
0036 }} // end namespace boost::hana
0037
0038 #endif // !BOOST_HANA_FWD_FOLD_HPP