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|---|---|---|
| 7c673cae FG |
1 | /*! |
| 2 | @file | |
| 3 | Forward declares `boost::hana::drop_while`. | |
| 4 | ||
| 5 | @copyright Louis Dionne 2013-2016 | |
| 6 | Distributed under the Boost Software License, Version 1.0. | |
| 7 | (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt) | |
| 8 | */ | |
| 9 | ||
| 10 | #ifndef BOOST_HANA_FWD_DROP_WHILE_HPP | |
| 11 | #define BOOST_HANA_FWD_DROP_WHILE_HPP | |
| 12 | ||
| 13 | #include <boost/hana/config.hpp> | |
| 14 | #include <boost/hana/core/when.hpp> | |
| 15 | ||
| 16 | ||
| 17 | BOOST_HANA_NAMESPACE_BEGIN | |
| 18 | //! Drop elements from an iterable up to, but excluding, the first | |
| 19 | //! element for which the `predicate` is not satisfied. | |
| 20 | //! @ingroup group-Iterable | |
| 21 | //! | |
| 22 | //! Specifically, `drop_while` returns an iterable containing all the | |
| 23 | //! elements of the original iterable except for those in the range | |
| 24 | //! delimited by [`head`, `e`), where `head` is the first element and | |
| 25 | //! `e` is the first element for which the `predicate` is not satisfied. | |
| 26 | //! If the iterable is not finite, the `predicate` has to return a false- | |
| 27 | //! valued `Logical` at a finite index for this method to return. | |
| 28 | //! | |
| 29 | //! | |
| 30 | //! @param iterable | |
| 31 | //! The iterable from which elements are dropped. | |
| 32 | //! | |
| 33 | //! @param predicate | |
| 34 | //! A function called as `predicate(x)`, where `x` is an element of the | |
| 35 | //! structure, and returning a `Logical` representing whether `x` should | |
| 36 | //! be dropped from the structure. In the current version of the library, | |
| 37 | //! `predicate` should return a compile-time `Logical`. | |
| 38 | //! | |
| 39 | //! | |
| 40 | //! Example | |
| 41 | //! ------- | |
| 42 | //! @include example/drop_while.cpp | |
| 43 | #ifdef BOOST_HANA_DOXYGEN_INVOKED | |
| 44 | constexpr auto drop_while = [](auto&& iterable, auto&& predicate) { | |
| 45 | return tag-dispatched; | |
| 46 | }; | |
| 47 | #else | |
| 48 | template <typename It, typename = void> | |
| 49 | struct drop_while_impl : drop_while_impl<It, when<true>> { }; | |
| 50 | ||
| 51 | struct drop_while_t { | |
| 52 | template <typename Xs, typename Pred> | |
| 53 | constexpr auto operator()(Xs&& xs, Pred&& pred) const; | |
| 54 | }; | |
| 55 | ||
| 56 | constexpr drop_while_t drop_while{}; | |
| 57 | #endif | |
| 58 | BOOST_HANA_NAMESPACE_END | |
| 59 | ||
| 60 | #endif // !BOOST_HANA_FWDDROP_WHILE_HPP |