89 lines
2.5 KiB
C++
89 lines
2.5 KiB
C++
/*
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* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/.
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*
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* Copyright 2010-2018 Danny Robson <danny@nerdcruft.net>
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*/
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#pragma once
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namespace cruft::iterator {
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///////////////////////////////////////////////////////////////////////////
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/// an iterator that can be infinitely incremented but never assigned.
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///
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/// useful for iterator ranges where the begin iterator is an output
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/// iterator and hence never reaches an end point (and where we don't want
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/// to engineer the client code to account for this).
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template <
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typename ValueT,
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typename CategoryT,
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typename DistanceT,
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typename PointerT,
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typename ReferenceT
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>
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struct unequal_iterator {
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using value_type = ValueT;
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using iterator_category = CategoryT;
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using difference_type = DistanceT;
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using pointer = PointerT;
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using reference = ReferenceT;
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unequal_iterator& operator++ ( ) { return *this; }
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unequal_iterator operator++ (int) { return *this; }
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};
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//-------------------------------------------------------------------------
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template <typename ContainerT>
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auto
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make_unequal_iterator (const ContainerT&)
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{
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using t = typename std::iterator_traits<typename ContainerT::iterator>;
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return unequal_iterator<
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typename t::value_type,
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typename t::iterator_category,
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typename t::difference_type,
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typename t::pointer,
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typename t::reference
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> {};
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};
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//-------------------------------------------------------------------------
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template <
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typename OtherT,
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typename ValueT,
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typename CategoryT,
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typename DistanceT,
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typename PointerT,
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typename ReferenceT>
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constexpr bool
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operator== (
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const unequal_iterator<ValueT,CategoryT,DistanceT,PointerT,ReferenceT>&,
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const OtherT&
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) {
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return false;
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}
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//-------------------------------------------------------------------------
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template <
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typename OtherT,
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typename ValueT,
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typename CategoryT,
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typename DistanceT,
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typename PointerT,
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typename ReferenceT>
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constexpr bool
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operator== (
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const OtherT&,
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const unequal_iterator<ValueT,CategoryT,DistanceT,PointerT,ReferenceT>&
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) {
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return false;
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}
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}
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