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more/gen/view.h

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//  Copyright (C) 2000--2001  Petter Urkedal (petter.urkedal@matfys.lth.se)
//
//  This file is free software; you can redistribute it and/or modify
//  it under the terms of the GNU General Public License as published by
//  the Free Software Foundation; either version 2 of the License, or
//  (at your option) any later version.
//
//  This file is distributed in the hope that it will be useful,
//  but WITHOUT ANY WARRANTY; without even the implied warranty of
//  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
//  GNU General Public License for more details.
//
//  You should have received a copy of the GNU General Public License
//  along with this program; if not, write to the Free Software
//  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
//
//  As a special exception, you may use this file as part of a free
//  software library without restriction.  Specifically, if other files
//  instantiate templates or use macros or inline functions from this
//  file, or you compile this file and link it with other files to
//  produce an executable, this file does not by itself cause the
//  resulting executable to be covered by the GNU General Public
//  License.  This exception does not however invalidate any other
//  reasons why the executable file might be covered by the GNU General
//  Public License.
//
//  $Id: view.h,v 1.1 2002/05/30 18:01:37 petter_urkedal Exp $


#ifndef MORE_GEN_VIEW_H
#define MORE_GEN_VIEW_H

#include <iterator>


namespace more {
namespace gen {

  //  TODO.  The two if-view assumes the subiterator is bidirectional
  //  or better, though if-views are meaningful also for forward and
  //  input iterators.

  template< typename Subiterator, typename Filter >
    struct if_view
    {
        typedef Subiterator subiterator;
        typedef std::iterator_traits<subiterator> subiterator_traits;
        typedef typename subiterator_traits::value_type value_type;

        struct iterator
            : std::iterator<std::bidirectional_iterator_tag, value_type>
        {
            typedef typename if_view::value_type value_type;
            typedef iterator self;

            iterator() {}
            iterator(if_view* context_,
                     subiterator subit_)
                : context(context_), subit(subit_) {}
            iterator(self const& it)
                : context(it.context), subit(it.subit) {}
            self& operator=(self const& rhs) {
                context = rhs.context;
                subit = rhs.subit;
                return *this;
            }

            bool operator==(self const& rhs) const
            { return subit == rhs.subit; }
            bool operator!=(self const& rhs) const
            { return subit != rhs.subit; }

            self& operator++() {
                do ++subit;
                while (subit != context->last && !context->test(*subit));
                return *this;
            }
            self operator++(int) {
                self tmp = *this;
                ++*this;
                return tmp;
            }
            self& operator--() {
                do --subit;
                while (subit != context->first && !context->test(*subit));
                return *this;
            }
            self operator--(int) {
                self tmp = *this;
                --*this;
                return tmp;
            }

            value_type operator*() { return *subit; }
            value_type* operator->() { return &(*subit); }

          private:
            if_view* context;
            subiterator subit;
        };

        if_view() {}
        if_view(Subiterator first_, Subiterator last_,
                     Filter const& test_)
            : first(first_), last(last_), test(test_) { fix_bounds(); }
        if_view(Subiterator first_, Subiterator last_)
            : first(first_), last(last_) { fix_bounds(); }
        if_view(if_view const& x)
            : first(x.first), last(x.last), test(x.test) {}
        if_view& operator=(if_view const& rhs) {
            first = rhs.first;
            last = rhs.last;
            test = rhs.test;
            return *this;
        }

        iterator begin() { return iterator(this, first); }
        iterator end() { return iterator(this, last); }
        subiterator sub_begin() { return first; }
        subiterator sub_end() { return last; }

      private:
        void fix_bounds() {
            while (first != last && !test(*first))  ++first;
            if (first != last) {
                --last;
                while (first != last && !test(*last))  --last;
                ++last;
            }
        }

        subiterator first, last;
        Filter test;
        friend class iterator;
    };

  template< typename Subiterator, typename Filter, typename Transform >
    struct transform_if_view
    {
        typedef Subiterator subiterator;
        typedef std::iterator_traits<subiterator> subiterator_traits;
        typedef typename Transform::result_type value_type;

        struct iterator
            : std::iterator<std::bidirectional_iterator_tag, value_type>
        {
            typedef typename transform_if_view::value_type value_type;
            typedef iterator self;

            iterator() {}
            iterator(transform_if_view* context_,
                     subiterator subit_)
                : context(context_), subit(subit_) {}
            iterator(self const& it)
                : context(it.context), subit(it.subit) {}
            self& operator=(self const& rhs) {
                context = rhs.context;
                subit = rhs.subit;
                return *this;
            }

            bool operator==(self const& rhs) const
            { return subit == rhs.subit; }
            bool operator!=(self const& rhs) const
            { return subit != rhs.subit; }

            self& operator++() {
                do ++subit;
                while (subit != context->last && !context->test(*subit));
                return *this;
            }
            self operator++(int) {
                self tmp = *this;
                ++*this;
                return tmp;
            }
            self& operator--() {
                do --subit;
                while (subit != context->first && !context->test(*subit));
                return *this;
            }
            self operator--(int) {
                self tmp = *this;
                --*this;
                return tmp;
            }

            value_type operator*() { return context->trn(*subit); }
            value_type* operator->() { return &(context->trn(*subit)); }

          private:
            transform_if_view* context;
            subiterator subit;
        };

        transform_if_view() {}
        transform_if_view(Subiterator first_, Subiterator last_,
                          Filter const& test_, Transform const& trn_)
            : first(first_), last(last_),
              test(test_), trn(trn_) { fix_bounds(); }
        transform_if_view(Subiterator first_, Subiterator last_,
                          Filter const& test_)
            : first(first_), last(last_), test(test_)  { fix_bounds(); }
        transform_if_view(Subiterator first_, Subiterator last_)
            : first(first_), last(last_) { fix_bounds(); }
        transform_if_view(transform_if_view const& x)
            : first(x.first), last(x.last), test(x.test) {}
        transform_if_view& operator=(transform_if_view const& rhs) {
            first = rhs.first;
            last = rhs.last;
            test = rhs.test;
            trn = rhs.trn;
            return *this;
        }

        iterator begin() { return iterator(this, first); }
        iterator end() { return iterator(this, last); }
        subiterator sub_begin() { return first; }
        subiterator sub_end() { return last; }

      private:
        void fix_bounds() {
            while (first != last && !test(*first))  ++first;
            if (first != last) {
                --last;
                while (first != last && !test(*last))  --last;
                ++last;
            }
        }

        subiterator first, last;
        Filter test;
        Transform trn;
        friend class iterator;
    };

}} // more::gen

#endif

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