73 lines
2.1 KiB
C++
73 lines
2.1 KiB
C++
/*!
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@file
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Forward declares `boost::hana::suffix`.
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@copyright Louis Dionne 2013-2016
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Distributed under the Boost Software License, Version 1.0.
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(See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
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*/
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#ifndef BOOST_HANA_FWD_SUFFIX_HPP
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#define BOOST_HANA_FWD_SUFFIX_HPP
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#include <boost/hana/config.hpp>
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#include <boost/hana/core/when.hpp>
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BOOST_HANA_NAMESPACE_BEGIN
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//! Inserts a value after each element of a monadic structure.
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//! @ingroup group-MonadPlus
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//!
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//! Given a monadic structure `xs` and a value `z` (called the suffix),
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//! `suffix` returns a new monadic structure such that
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//! @code
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//! suffix(xs, z) == flatten(transform(xs, [](auto x) {
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//! return concat(lift<M>(x), lift<M>(z));
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//! }))
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//! @endcode
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//!
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//! For sequences, this simply corresponds to inserting the suffix after
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//! each element of the sequence. For example, given a sequence
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//! `[x1, ..., xn]`, `suffix` will return
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//! @code
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//! [x1, z, x2, z, ..., xn, z]
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//! @endcode
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//! As explained above, this can be generalized to other MonadPlus models,
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//! with various levels of interest.
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//!
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//!
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//! Signature
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//! ---------
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//! Given a MonadPlus `M`, the signature is
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//! @f$ \mathtt{suffix} : M(T) \times T \to M(T) @f$.
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//!
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//! @param xs
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//! A monadic structure.
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//!
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//! @param sfx
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//! A value (the suffix) to insert after each element of a monadic
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//! structure.
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//!
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//!
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//! Example
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//! -------
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//! @include example/suffix.cpp
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#ifdef BOOST_HANA_DOXYGEN_INVOKED
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constexpr auto suffix = [](auto&& xs, auto&& sfx) {
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return tag-dispatched;
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};
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#else
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template <typename M, typename = void>
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struct suffix_impl : suffix_impl<M, when<true>> { };
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struct suffix_t {
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template <typename Xs, typename Sfx>
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constexpr auto operator()(Xs&& xs, Sfx&& sfx) const;
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};
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constexpr suffix_t suffix{};
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#endif
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BOOST_HANA_NAMESPACE_END
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#endif // !BOOST_HANA_FWD_SUFFIX_HPP
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