71 lines
2.2 KiB
C++
71 lines
2.2 KiB
C++
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/*!
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@file
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Forward declares `boost::hana::remove`.
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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_REMOVE_HPP
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#define BOOST_HANA_FWD_REMOVE_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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//! Remove all the elements of a monadic structure that are equal to some
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//! value.
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//! @ingroup group-MonadPlus
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//!
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//! Given a monadic structure `xs` and a `value`, `remove` returns a new
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//! monadic structure equal to `xs` without all its elements that are
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//! equal to the given `value`. `remove` is equivalent to `remove_if`
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//! with the `equal.to(value)` predicate, i.e.
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//! @code
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//! remove(xs, value) == remove_if(xs, equal.to(value))
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//! @endcode
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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` and a value of type `T`, the signature is
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//! \f$
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//! \mathrm{remove} : M(T) \times T \to M(T)
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//! \f$
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//!
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//! @param xs
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//! A monadic structure to remove some elements from.
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//!
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//! @param value
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//! A value that is compared to every element `x` of the structure.
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//! Elements of the structure that are equal to that value are removed
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//! from the structure. This requires every element to be Comparable
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//! with `value`. Furthermore, in the current version of the library,
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//! comparing `value` with any element of the structure must yield a
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//! compile-time Logical.
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//!
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//!
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//! Example
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//! -------
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//! @include example/remove.cpp
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#ifdef BOOST_HANA_DOXYGEN_INVOKED
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constexpr auto remove = [](auto&& xs, auto&& value) {
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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 remove_impl : remove_impl<M, when<true>> { };
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struct remove_t {
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template <typename Xs, typename Value>
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constexpr auto operator()(Xs&& xs, Value&& value) const;
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};
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constexpr remove_t remove{};
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#endif
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BOOST_HANA_NAMESPACE_END
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#endif // !BOOST_HANA_FWD_REMOVE_HPP
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