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Diffstat (limited to 'boost/hana/fwd/replicate.hpp')
-rw-r--r-- | boost/hana/fwd/replicate.hpp | 75 |
1 files changed, 75 insertions, 0 deletions
diff --git a/boost/hana/fwd/replicate.hpp b/boost/hana/fwd/replicate.hpp new file mode 100644 index 0000000000..0580d90601 --- /dev/null +++ b/boost/hana/fwd/replicate.hpp @@ -0,0 +1,75 @@ +/*! +@file +Forward declares `boost::hana::replicate`. + +@copyright Louis Dionne 2013-2016 +Distributed under the Boost Software License, Version 1.0. +(See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt) + */ + +#ifndef BOOST_HANA_FWD_REPLICATE_HPP +#define BOOST_HANA_FWD_REPLICATE_HPP + +#include <boost/hana/config.hpp> +#include <boost/hana/core/when.hpp> + + +BOOST_HANA_NAMESPACE_BEGIN + //! Create a monadic structure by combining a lifted value with itself + //! `n` times. + //! @ingroup group-MonadPlus + //! + //! Given a value `x`, a non-negative `IntegralConstant` `n` and the tag + //! of a monadic structure `M`, `replicate` creates a new monadic structure + //! which is the result of combining `x` with itself `n` times inside the + //! monadic structure. In other words, `replicate` simply `lift`s `x` into + //! the monadic structure, and then combines that with itself `n` times: + //! @code + //! replicate<M>(x, n) == cycle(lift<M>(x), n) + //! @endcode + //! + //! If `n` is zero, then the identity of the `concat` operation is returned. + //! In the case of sequences, this corresponds to creating a new sequence + //! holding `n` copies of `x`. + //! + //! + //! Signature + //! --------- + //! Given an `IntegralConstant` `C` and MonadPlus `M`, the signature is + //! @f$ \mathtt{replicate}_M : T \times C \to M(T) @f$. + //! + //! @tparam M + //! The tag of the returned monadic structure. It must be a + //! model of the MonadPlus concept. + //! + //! @param x + //! The value to lift into a monadic structure and then combine with + //! itself. + //! + //! @param n + //! A non-negative `IntegralConstant` representing the number of times to + //! combine `lift<M>(x)` with itself. If `n == 0`, `replicate` returns + //! `empty<M>()`. + //! + //! + //! Example + //! ------- + //! @include example/replicate.cpp +#ifdef BOOST_HANA_DOXYGEN_INVOKED + template <typename M> + constexpr auto replicate = [](auto&& x, auto const& n) { + return tag-dispatched; + }; +#else + template <typename M, typename = void> + struct replicate_impl : replicate_impl<M, when<true>> { }; + + template <typename M> + struct replicate_t; + + template <typename M> + constexpr replicate_t<M> replicate{}; +#endif +BOOST_HANA_NAMESPACE_END + +#endif // !BOOST_HANA_FWD_REPLICATE_HPP |