56 lines
1.5 KiB
C++
56 lines
1.5 KiB
C++
/*!
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@file
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Forward declares `boost::hana::for_each`.
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@copyright Louis Dionne 2013-2017
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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_FOR_EACH_HPP
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#define BOOST_HANA_FWD_FOR_EACH_HPP
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#include <boost/hana/config.hpp>
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#include <boost/hana/core/when.hpp>
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namespace boost { namespace hana {
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//! Perform an action on each element of a foldable, discarding
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//! the result each time.
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//! @ingroup group-Foldable
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//!
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//! Iteration is done from left to right, i.e. in the same order as when
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//! using `fold_left`. If the structure is not finite, this method will
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//! not terminate.
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//!
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//!
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//! @param xs
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//! The structure to iterate over.
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//!
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//! @param f
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//! A function called as `f(x)` for each element `x` of the structure.
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//! The result of `f(x)`, whatever it is, is ignored.
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//!
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//!
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//! Example
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//! -------
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//! @include example/for_each.cpp
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#ifdef BOOST_HANA_DOXYGEN_INVOKED
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constexpr auto for_each = [](auto&& xs, auto&& f) -> void {
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tag-dispatched;
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};
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#else
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template <typename T, typename = void>
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struct for_each_impl : for_each_impl<T, when<true>> { };
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struct for_each_t {
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template <typename Xs, typename F>
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constexpr void operator()(Xs&& xs, F&& f) const;
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};
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BOOST_HANA_INLINE_VARIABLE constexpr for_each_t for_each{};
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#endif
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}} // end namespace boost::hana
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#endif // !BOOST_HANA_FWD_FOR_EACH_HPP
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