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