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- /*!
- @file
- Forward declares `boost::hana::drop_while`.
- @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_DROP_WHILE_HPP
- #define BOOST_HANA_FWD_DROP_WHILE_HPP
- #include <boost/hana/config.hpp>
- #include <boost/hana/core/when.hpp>
- BOOST_HANA_NAMESPACE_BEGIN
- //! Drop elements from an iterable up to, but excluding, the first
- //! element for which the `predicate` is not satisfied.
- //! @ingroup group-Iterable
- //!
- //! Specifically, `drop_while` returns an iterable containing all the
- //! elements of the original iterable except for those in the range
- //! delimited by [`head`, `e`), where `head` is the first element and
- //! `e` is the first element for which the `predicate` is not satisfied.
- //! If the iterable is not finite, the `predicate` has to return a false-
- //! valued `Logical` at a finite index for this method to return.
- //!
- //!
- //! @param iterable
- //! The iterable from which elements are dropped.
- //!
- //! @param predicate
- //! A function called as `predicate(x)`, where `x` is an element of the
- //! structure, and returning a `Logical` representing whether `x` should
- //! be dropped from the structure. In the current version of the library,
- //! `predicate` should return a compile-time `Logical`.
- //!
- //!
- //! Example
- //! -------
- //! @include example/drop_while.cpp
- #ifdef BOOST_HANA_DOXYGEN_INVOKED
- constexpr auto drop_while = [](auto&& iterable, auto&& predicate) {
- return tag-dispatched;
- };
- #else
- template <typename It, typename = void>
- struct drop_while_impl : drop_while_impl<It, when<true>> { };
- struct drop_while_t {
- template <typename Xs, typename Pred>
- constexpr auto operator()(Xs&& xs, Pred&& pred) const;
- };
- constexpr drop_while_t drop_while{};
- #endif
- BOOST_HANA_NAMESPACE_END
- #endif // !BOOST_HANA_FWDDROP_WHILE_HPP
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