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