76 lines
2.4 KiB
C++
76 lines
2.4 KiB
C++
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/*!
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@file
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Forward declares `boost::hana::replicate`.
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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_REPLICATE_HPP
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#define BOOST_HANA_FWD_REPLICATE_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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//! Create a monadic structure by combining a lifted value with itself
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//! `n` times.
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//! @ingroup group-MonadPlus
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//!
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//! Given a value `x`, a non-negative `IntegralConstant` `n` and the tag
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//! of a monadic structure `M`, `replicate` creates a new monadic structure
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//! which is the result of combining `x` with itself `n` times inside the
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//! monadic structure. In other words, `replicate` simply `lift`s `x` into
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//! the monadic structure, and then combines that with itself `n` times:
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//! @code
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//! replicate<M>(x, n) == cycle(lift<M>(x), n)
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//! @endcode
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//!
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//! If `n` is zero, then the identity of the `concat` operation is returned.
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//! In the case of sequences, this corresponds to creating a new sequence
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//! holding `n` copies of `x`.
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//!
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//!
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//! Signature
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//! ---------
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//! Given an `IntegralConstant` `C` and MonadPlus `M`, the signature is
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//! @f$ \mathtt{replicate}_M : T \times C \to M(T) @f$.
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//!
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//! @tparam M
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//! The tag of the returned monadic structure. It must be a
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//! model of the MonadPlus concept.
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//!
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//! @param x
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//! The value to lift into a monadic structure and then combine with
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//! itself.
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//!
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//! @param n
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//! A non-negative `IntegralConstant` representing the number of times to
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//! combine `lift<M>(x)` with itself. If `n == 0`, `replicate` returns
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//! `empty<M>()`.
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//!
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//!
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//! Example
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//! -------
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//! @include example/replicate.cpp
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#ifdef BOOST_HANA_DOXYGEN_INVOKED
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template <typename M>
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constexpr auto replicate = [](auto&& x, auto const& n) {
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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 replicate_impl : replicate_impl<M, when<true>> { };
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template <typename M>
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struct replicate_t;
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template <typename M>
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constexpr replicate_t<M> replicate{};
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#endif
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BOOST_HANA_NAMESPACE_END
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#endif // !BOOST_HANA_FWD_REPLICATE_HPP
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