tree.h

//  STL-like templated tree class.
//
// Copyright (C) 2001-2009 Kasper Peeters <kasper.peeters@aei.mpg.de>
// Distributed under the GNU General Public License version 3,
// (eventually to be changed to the Boost Software License).

#ifndef tree_hh_
#define tree_hh_

#include <cassert>
#include <memory>
#include <stdexcept>
#include <iterator>
#include <set>
#include <queue>
#include <algorithm>
#include <stddef.h>

// HP-style construct/destroy have gone from the standard,
// so here is a copy.

namespace kp {

template <class T1, class T2>
void constructor(T1* p, T2& val) 
    {
    new ((void *) p) T1(val);
    }

template <class T1>
void constructor(T1* p) 
    {
    new ((void *) p) T1;
    }

template <class T1>
void destructor(T1* p)
    {
    p->~T1();
    }

}

template<class T>
class tree_node_ { // size: 5*4=20 bytes (on 32 bit arch), can be reduced by 8.
    public:
        tree_node_<T> *parent;
       tree_node_<T> *first_child, *last_child;
        tree_node_<T> *prev_sibling, *next_sibling;
        T data;
}; // __attribute__((packed));

template <class T, class tree_node_allocator = std::allocator<tree_node_<T> > >
class tree {
    protected:
        typedef tree_node_<T> tree_node;
    public:
        typedef T value_type;

        class iterator_base;
        class pre_order_iterator;
        class post_order_iterator;
        class sibling_iterator;
      class leaf_iterator;

        tree();
        tree(const T&);
        tree(const iterator_base&);
        tree(const tree<T, tree_node_allocator>&);
        ~tree();
        void operator=(const tree<T, tree_node_allocator>&);

#ifdef __SGI_STL_PORT
        class iterator_base : public stlport::bidirectional_iterator<T, ptrdiff_t> {
#else
        class iterator_base {
#endif
            public:
                typedef T                               value_type;
                typedef T*                              pointer;
                typedef T&                              reference;
                typedef size_t                          size_type;
                typedef ptrdiff_t                       difference_type;
                typedef std::bidirectional_iterator_tag iterator_category;

                iterator_base();
                iterator_base(tree_node *);

                T&             operator*() const;
                T*             operator->() const;

                void         skip_children();
                void         skip_children(bool skip);
                unsigned int number_of_children() const;

                sibling_iterator begin() const;
                sibling_iterator end() const;

                tree_node *node;
            protected:
                bool skip_current_children_;
        };

        class pre_order_iterator : public iterator_base { 
            public:
                pre_order_iterator();
                pre_order_iterator(tree_node *);
                pre_order_iterator(const iterator_base&);
                pre_order_iterator(const sibling_iterator&);

                bool    operator==(const pre_order_iterator&) const;
                bool    operator!=(const pre_order_iterator&) const;
                pre_order_iterator&  operator++();
               pre_order_iterator&  operator--();
                pre_order_iterator   operator++(int);
                pre_order_iterator   operator--(int);
                pre_order_iterator&  operator+=(unsigned int);
                pre_order_iterator&  operator-=(unsigned int);
        };

        class post_order_iterator : public iterator_base {
            public:
                post_order_iterator();
                post_order_iterator(tree_node *);
                post_order_iterator(const iterator_base&);
                post_order_iterator(const sibling_iterator&);

                bool    operator==(const post_order_iterator&) const;
                bool    operator!=(const post_order_iterator&) const;
                post_order_iterator&  operator++();
               post_order_iterator&  operator--();
                post_order_iterator   operator++(int);
                post_order_iterator   operator--(int);
                post_order_iterator&  operator+=(unsigned int);
                post_order_iterator&  operator-=(unsigned int);

                void descend_all();
        };

        class breadth_first_queued_iterator : public iterator_base {
            public:
                breadth_first_queued_iterator();
                breadth_first_queued_iterator(tree_node *);
                breadth_first_queued_iterator(const iterator_base&);

                bool    operator==(const breadth_first_queued_iterator&) const;
                bool    operator!=(const breadth_first_queued_iterator&) const;
                breadth_first_queued_iterator&  operator++();
                breadth_first_queued_iterator   operator++(int);
                breadth_first_queued_iterator&  operator+=(unsigned int);

            private:
                std::queue<tree_node *> traversal_queue;
        };

        typedef pre_order_iterator            iterator;
        typedef breadth_first_queued_iterator breadth_first_iterator;

        class fixed_depth_iterator : public iterator_base {
            public:
                fixed_depth_iterator();
                fixed_depth_iterator(tree_node *);
                fixed_depth_iterator(const iterator_base&);
                fixed_depth_iterator(const sibling_iterator&);
                fixed_depth_iterator(const fixed_depth_iterator&);

                bool    operator==(const fixed_depth_iterator&) const;
                bool    operator!=(const fixed_depth_iterator&) const;
                fixed_depth_iterator&  operator++();
               fixed_depth_iterator&  operator--();
                fixed_depth_iterator   operator++(int);
                fixed_depth_iterator   operator--(int);
                fixed_depth_iterator&  operator+=(unsigned int);
                fixed_depth_iterator&  operator-=(unsigned int);

                tree_node *top_node;
        };

        class sibling_iterator : public iterator_base {
            public:
                sibling_iterator();
                sibling_iterator(tree_node *);
                sibling_iterator(const sibling_iterator&);
                sibling_iterator(const iterator_base&);

                bool    operator==(const sibling_iterator&) const;
                bool    operator!=(const sibling_iterator&) const;
                sibling_iterator&  operator++();
                sibling_iterator&  operator--();
                sibling_iterator   operator++(int);
                sibling_iterator   operator--(int);
                sibling_iterator&  operator+=(unsigned int);
                sibling_iterator&  operator-=(unsigned int);

                tree_node *range_first() const;
                tree_node *range_last() const;
                tree_node *parent_;
            private:
                void set_parent_();
        };

      class leaf_iterator : public iterator_base {
         public:
            leaf_iterator();
            leaf_iterator(tree_node *, tree_node *top=0);
            leaf_iterator(const sibling_iterator&);
            leaf_iterator(const iterator_base&);

            bool    operator==(const leaf_iterator&) const;
            bool    operator!=(const leaf_iterator&) const;
            leaf_iterator&  operator++();
            leaf_iterator&  operator--();
            leaf_iterator   operator++(int);
            leaf_iterator   operator--(int);
            leaf_iterator&  operator+=(unsigned int);
            leaf_iterator&  operator-=(unsigned int);
            private:
                tree_node *top_node;
      };

        inline pre_order_iterator   begin() const;
        inline pre_order_iterator   end() const;
        post_order_iterator  begin_post() const;
        post_order_iterator  end_post() const;
        fixed_depth_iterator begin_fixed(const iterator_base&, unsigned int) const;
        fixed_depth_iterator end_fixed(const iterator_base&, unsigned int) const;
        breadth_first_queued_iterator begin_breadth_first() const;
        breadth_first_queued_iterator end_breadth_first() const;
        sibling_iterator     begin(const iterator_base&) const;
        sibling_iterator     end(const iterator_base&) const;
      leaf_iterator   begin_leaf() const;
      leaf_iterator   end_leaf() const;
      leaf_iterator   begin_leaf(const iterator_base& top) const;
      leaf_iterator   end_leaf(const iterator_base& top) const;

        template<typename   iter> static iter parent(iter);
        template<typename iter> iter previous_sibling(iter) const;
        template<typename iter> iter next_sibling(iter) const;
        template<typename iter> iter next_at_same_depth(iter) const;

        void     clear();
        template<typename iter> iter erase(iter);
        void     erase_children(const iterator_base&);

        template<typename iter> iter append_child(iter position); 
        template<typename iter> iter prepend_child(iter position); 
        template<typename iter> iter append_child(iter position, const T& x);
        template<typename iter> iter prepend_child(iter position, const T& x);
        template<typename iter> iter append_child(iter position, iter other_position);
        template<typename iter> iter prepend_child(iter position, iter other_position);
        template<typename iter> iter append_children(iter position, sibling_iterator from, sibling_iterator to);
        template<typename iter> iter prepend_children(iter position, sibling_iterator from, sibling_iterator to);

        pre_order_iterator set_head(const T& x);
        template<typename iter> iter insert(iter position, const T& x);
        sibling_iterator insert(sibling_iterator position, const T& x);
        template<typename iter> iter insert_subtree(iter position, const iterator_base& subtree);
        template<typename iter> iter insert_after(iter position, const T& x);
        template<typename iter> iter insert_subtree_after(iter position, const iterator_base& subtree);

        template<typename iter> iter replace(iter position, const T& x);
        template<typename iter> iter replace(iter position, const iterator_base& from);
        sibling_iterator replace(sibling_iterator orig_begin, sibling_iterator orig_end, 
                                         sibling_iterator new_begin,  sibling_iterator new_end); 

        template<typename iter> iter flatten(iter position);
        template<typename iter> iter reparent(iter position, sibling_iterator begin, sibling_iterator end);
        template<typename iter> iter reparent(iter position, iter from);

        template<typename iter> iter wrap(iter position, const T& x);

        template<typename iter> iter move_after(iter target, iter source);
      template<typename iter> iter move_before(iter target, iter source);
      sibling_iterator move_before(sibling_iterator target, sibling_iterator source);
        template<typename iter> iter move_ontop(iter target, iter source);

        void     merge(sibling_iterator, sibling_iterator, sibling_iterator, sibling_iterator, 
                            bool duplicate_leaves=false);
        void     sort(sibling_iterator from, sibling_iterator to, bool deep=false);
        template<class StrictWeakOrdering>
        void     sort(sibling_iterator from, sibling_iterator to, StrictWeakOrdering comp, bool deep=false);
        template<typename iter>
        bool     equal(const iter& one, const iter& two, const iter& three) const;
        template<typename iter, class BinaryPredicate>
        bool     equal(const iter& one, const iter& two, const iter& three, BinaryPredicate) const;
        template<typename iter>
        bool     equal_subtree(const iter& one, const iter& two) const;
        template<typename iter, class BinaryPredicate>
        bool     equal_subtree(const iter& one, const iter& two, BinaryPredicate) const;
        tree     subtree(sibling_iterator from, sibling_iterator to) const;
        void     subtree(tree&, sibling_iterator from, sibling_iterator to) const;
        void     swap(sibling_iterator it);
       void     swap(iterator, iterator);
        
        size_t   size() const;
        size_t   size(const iterator_base&) const;
        bool     empty() const;
        static int depth(const iterator_base&);
        static int depth(const iterator_base&, const iterator_base&);
        int      max_depth() const;
        int      max_depth(const iterator_base&) const;
        static unsigned int number_of_children(const iterator_base&);
        unsigned int number_of_siblings(const iterator_base&) const;
        bool     is_in_subtree(const iterator_base& position, const iterator_base& begin, 
                                      const iterator_base& end) const;
        bool     is_valid(const iterator_base&) const;

        unsigned int index(sibling_iterator it) const;
        static sibling_iterator child(const iterator_base& position, unsigned int);
        sibling_iterator sibling(const iterator_base& position, unsigned int);                  
        
        class iterator_base_less {
            public:
                bool operator()(const typename tree<T, tree_node_allocator>::iterator_base& one,
                                     const typename tree<T, tree_node_allocator>::iterator_base& two) const
                    {
                    return one.node < two.node;
                    }
        };
        tree_node *head, *feet;    // head/feet are always dummy; if an iterator points to them it is invalid
    private:
        tree_node_allocator alloc_;
        void head_initialise_();
        void copy_(const tree<T, tree_node_allocator>& other);

        template<class StrictWeakOrdering>
        class compare_nodes {
            public:
                compare_nodes(StrictWeakOrdering comp) : comp_(comp) {};
                
                bool operator()(const tree_node *a, const tree_node *b) 
                    {
                    return comp_(a->data, b->data);
                    }
            private:
                StrictWeakOrdering comp_;
        };
};

//template <class T, class tree_node_allocator>
//class iterator_base_less {
//  public:
//      bool operator()(const typename tree<T, tree_node_allocator>::iterator_base& one,
//                        const typename tree<T, tree_node_allocator>::iterator_base& two) const
//          {
//          txtout << "operatorclass<" << one.node < two.node << std::endl;
//          return one.node < two.node;
//          }
//};

// template <class T, class tree_node_allocator>
// bool operator<(const typename tree<T, tree_node_allocator>::iterator& one,
//                  const typename tree<T, tree_node_allocator>::iterator& two)
//  {
//  txtout << "operator< " << one.node < two.node << std::endl;
//  if(one.node < two.node) return true;
//  return false;
//  }
// 
// template <class T, class tree_node_allocator>
// bool operator==(const typename tree<T, tree_node_allocator>::iterator& one,
//                  const typename tree<T, tree_node_allocator>::iterator& two)
//  {
//  txtout << "operator== " << one.node == two.node << std::endl;
//  if(one.node == two.node) return true;
//  return false;
//  }
// 
// template <class T, class tree_node_allocator>
// bool operator>(const typename tree<T, tree_node_allocator>::iterator_base& one,
//                  const typename tree<T, tree_node_allocator>::iterator_base& two)
//  {
//  txtout << "operator> " << one.node < two.node << std::endl;
//  if(one.node > two.node) return true;
//  return false;
//  }



// Tree

template <class T, class tree_node_allocator>
tree<T, tree_node_allocator>::tree() 
    {
    head_initialise_();
    }

template <class T, class tree_node_allocator>
tree<T, tree_node_allocator>::tree(const T& x) 
    {
    head_initialise_();
    set_head(x);
    }

template <class T, class tree_node_allocator>
tree<T, tree_node_allocator>::tree(const iterator_base& other)
    {
    head_initialise_();
    set_head((*other));
    replace(begin(), other);
    }

template <class T, class tree_node_allocator>
tree<T, tree_node_allocator>::~tree()
    {
    clear();
    alloc_.deallocate(head,1);
    alloc_.deallocate(feet,1);
    }

template <class T, class tree_node_allocator>
void tree<T, tree_node_allocator>::head_initialise_() 
   { 
   head = alloc_.allocate(1,0); // MSVC does not have default second argument 
    feet = alloc_.allocate(1,0);

   head->parent=0;
   head->first_child=0;
   head->last_child=0;
   head->prev_sibling=0; //head;
   head->next_sibling=feet; //head;

    feet->parent=0;
    feet->first_child=0;
    feet->last_child=0;
    feet->prev_sibling=head;
    feet->next_sibling=0;
   }

template <class T, class tree_node_allocator>
void tree<T, tree_node_allocator>::operator=(const tree<T, tree_node_allocator>& other)
    {
    copy_(other);
    }

template <class T, class tree_node_allocator>
tree<T, tree_node_allocator>::tree(const tree<T, tree_node_allocator>& other)
    {
    head_initialise_();
    copy_(other);
    }

template <class T, class tree_node_allocator>
void tree<T, tree_node_allocator>::copy_(const tree<T, tree_node_allocator>& other) 
    {
    clear();
    pre_order_iterator it=other.begin(), to=begin();
    while(it!=other.end()) {
        to=insert(to, (*it));
        it.skip_children();
        ++it;
        }
    to=begin();
    it=other.begin();
    while(it!=other.end()) {
        to=replace(to, it);
        to.skip_children();
        it.skip_children();
        ++to;
        ++it;
        }
    }

template <class T, class tree_node_allocator>
void tree<T, tree_node_allocator>::clear()
    {
    if(head)
        while(head->next_sibling!=feet)
            erase(pre_order_iterator(head->next_sibling));
    }

template<class T, class tree_node_allocator> 
void tree<T, tree_node_allocator>::erase_children(const iterator_base& it)
    {
//  std::cout << "erase_children " << it.node << std::endl;
    if(it.node==0) return;

    tree_node *cur=it.node->first_child;
    tree_node *prev=0;

    while(cur!=0) {
        prev=cur;
        cur=cur->next_sibling;
        erase_children(pre_order_iterator(prev));
        kp::destructor(&prev->data);
        alloc_.deallocate(prev,1);
        }
    it.node->first_child=0;
    it.node->last_child=0;
//  std::cout << "exit" << std::endl;
    }

template<class T, class tree_node_allocator> 
template<class iter>
iter tree<T, tree_node_allocator>::erase(iter it)
    {
    tree_node *cur=it.node;
    assert(cur!=head);
    iter ret=it;
    ret.skip_children();
    ++ret;
    erase_children(it);
    if(cur->prev_sibling==0) {
        cur->parent->first_child=cur->next_sibling;
        }
    else {
        cur->prev_sibling->next_sibling=cur->next_sibling;
        }
    if(cur->next_sibling==0) {
        cur->parent->last_child=cur->prev_sibling;
        }
    else {
        cur->next_sibling->prev_sibling=cur->prev_sibling;
        }

    kp::destructor(&cur->data);
   alloc_.deallocate(cur,1);
    return ret;
    }

template <class T, class tree_node_allocator>
typename tree<T, tree_node_allocator>::pre_order_iterator tree<T, tree_node_allocator>::begin() const
    {
    return pre_order_iterator(head->next_sibling);
    }

template <class T, class tree_node_allocator>
typename tree<T, tree_node_allocator>::pre_order_iterator tree<T, tree_node_allocator>::end() const
    {
    return pre_order_iterator(feet);
    }

template <class T, class tree_node_allocator>
typename tree<T, tree_node_allocator>::breadth_first_queued_iterator tree<T, tree_node_allocator>::begin_breadth_first() const
    {
    return breadth_first_queued_iterator(head->next_sibling);
    }

template <class T, class tree_node_allocator>
typename tree<T, tree_node_allocator>::breadth_first_queued_iterator tree<T, tree_node_allocator>::end_breadth_first() const
    {
    return breadth_first_queued_iterator();
    }

template <class T, class tree_node_allocator>
typename tree<T, tree_node_allocator>::post_order_iterator tree<T, tree_node_allocator>::begin_post() const
    {
    tree_node *tmp=head->next_sibling;
    if(tmp!=feet) {
        while(tmp->first_child)
            tmp=tmp->first_child;
        }
    return post_order_iterator(tmp);
    }

template <class T, class tree_node_allocator>
typename tree<T, tree_node_allocator>::post_order_iterator tree<T, tree_node_allocator>::end_post() const
    {
    return post_order_iterator(feet);
    }

template <class T, class tree_node_allocator>
typename tree<T, tree_node_allocator>::fixed_depth_iterator tree<T, tree_node_allocator>::begin_fixed(const iterator_base& pos, unsigned int dp) const
    {
    typename tree<T, tree_node_allocator>::fixed_depth_iterator ret;
    ret.top_node=pos.node;

    tree_node *tmp=pos.node;
    unsigned int curdepth=0;
    while(curdepth<dp) { // go down one level
        while(tmp->first_child==0) {
            if(tmp->next_sibling==0) {
                // try to walk up and then right again
                do {
                    if(tmp==ret.top_node)
                       throw std::range_error("tree: begin_fixed out of range");
                    tmp=tmp->parent;
               if(tmp==0) 
                       throw std::range_error("tree: begin_fixed out of range");
               --curdepth;
                   } while(tmp->next_sibling==0);
                }
            tmp=tmp->next_sibling;
            }
        tmp=tmp->first_child;
        ++curdepth;
        }

    ret.node=tmp;
    return ret;
    }

template <class T, class tree_node_allocator>
typename tree<T, tree_node_allocator>::fixed_depth_iterator tree<T, tree_node_allocator>::end_fixed(const iterator_base& pos, unsigned int dp) const
    {
    assert(1==0); // FIXME: not correct yet: use is_valid() as a temporary workaround 
    tree_node *tmp=pos.node;
    unsigned int curdepth=1;
    while(curdepth<dp) { // go down one level
        while(tmp->first_child==0) {
            tmp=tmp->next_sibling;
            if(tmp==0)
                throw std::range_error("tree: end_fixed out of range");
            }
        tmp=tmp->first_child;
        ++curdepth;
        }
    return tmp;
    }

template <class T, class tree_node_allocator>
typename tree<T, tree_node_allocator>::sibling_iterator tree<T, tree_node_allocator>::begin(const iterator_base& pos) const
    {
    assert(pos.node!=0);
    if(pos.node->first_child==0) {
        return end(pos);
        }
    return pos.node->first_child;
    }

template <class T, class tree_node_allocator>
typename tree<T, tree_node_allocator>::sibling_iterator tree<T, tree_node_allocator>::end(const iterator_base& pos) const
    {
    sibling_iterator ret(0);
    ret.parent_=pos.node;
    return ret;
    }

template <class T, class tree_node_allocator>
typename tree<T, tree_node_allocator>::leaf_iterator tree<T, tree_node_allocator>::begin_leaf() const
   {
   tree_node *tmp=head->next_sibling;
   if(tmp!=feet) {
      while(tmp->first_child)
         tmp=tmp->first_child;
      }
   return leaf_iterator(tmp);
   }

template <class T, class tree_node_allocator>
typename tree<T, tree_node_allocator>::leaf_iterator tree<T, tree_node_allocator>::end_leaf() const
   {
   return leaf_iterator(feet);
   }

template <class T, class tree_node_allocator>
typename tree<T, tree_node_allocator>::leaf_iterator tree<T, tree_node_allocator>::begin_leaf(const iterator_base& top) const
   {
    tree_node *tmp=top.node;
    while(tmp->first_child)
         tmp=tmp->first_child;
   return leaf_iterator(tmp, top.node);
   }

template <class T, class tree_node_allocator>
typename tree<T, tree_node_allocator>::leaf_iterator tree<T, tree_node_allocator>::end_leaf(const iterator_base& top) const
   {
   return leaf_iterator(top.node, top.node);
   }

template <class T, class tree_node_allocator>
template <typename iter>
iter tree<T, tree_node_allocator>::parent(iter position) 
    {
    assert(position.node!=0);
    return iter(position.node->parent);
    }

template <class T, class tree_node_allocator>
template <typename iter>
iter tree<T, tree_node_allocator>::previous_sibling(iter position) const
    {
    assert(position.node!=0);
    iter ret(position);
    ret.node=position.node->prev_sibling;
    return ret;
    }

template <class T, class tree_node_allocator>
template <typename iter>
iter tree<T, tree_node_allocator>::next_sibling(iter position) const
    {
    assert(position.node!=0);
    iter ret(position);
    ret.node=position.node->next_sibling;
    return ret;
    }

template <class T, class tree_node_allocator>
template <typename iter>
iter tree<T, tree_node_allocator>::next_at_same_depth(iter position) const
    {
    // We make use of a temporary fixed_depth iterator to implement this.

    typename tree<T, tree_node_allocator>::fixed_depth_iterator tmp(position.node);

    ++tmp;
    return iter(tmp);

//  assert(position.node!=0);
//  iter ret(position);
//
//  if(position.node->next_sibling) {
//      ret.node=position.node->next_sibling;
//      }
//  else { 
//      int relative_depth=0;
//     upper:
//      do {
//          ret.node=ret.node->parent;
//          if(ret.node==0) return ret;
//          --relative_depth;
//          } while(ret.node->next_sibling==0);
//     lower:
//      ret.node=ret.node->next_sibling;
//      while(ret.node->first_child==0) {
//          if(ret.node->next_sibling==0)
//              goto upper;
//          ret.node=ret.node->next_sibling;
//          if(ret.node==0) return ret;
//          }
//      while(relative_depth<0 && ret.node->first_child!=0) {
//          ret.node=ret.node->first_child;
//          ++relative_depth;
//          }
//      if(relative_depth<0) {
//          if(ret.node->next_sibling==0) goto upper;
//          else                          goto lower;
//          }
//      }
//  return ret;
    }

template <class T, class tree_node_allocator>
template <typename iter>
iter tree<T, tree_node_allocator>::append_child(iter position)
    {
    assert(position.node!=head);
    assert(position.node);

    tree_node *tmp=alloc_.allocate(1,0);
    kp::constructor(&tmp->data);
    tmp->first_child=0;
    tmp->last_child=0;

    tmp->parent=position.node;
    if(position.node->last_child!=0) {
        position.node->last_child->next_sibling=tmp;
        }
    else {
        position.node->first_child=tmp;
        }
    tmp->prev_sibling=position.node->last_child;
    position.node->last_child=tmp;
    tmp->next_sibling=0;
    return tmp;
    }

template <class T, class tree_node_allocator>
template <typename iter>
iter tree<T, tree_node_allocator>::prepend_child(iter position)
    {
    assert(position.node!=head);
    assert(position.node);

    tree_node *tmp=alloc_.allocate(1,0);
    kp::constructor(&tmp->data);
    tmp->first_child=0;
    tmp->last_child=0;

    tmp->parent=position.node;
    if(position.node->first_child!=0) {
        position.node->first_child->prev_sibling=tmp;
        }
    else {
        position.node->last_child=tmp;
        }
    tmp->next_sibling=position.node->first_child;
    position.node->prev_child=tmp;
    tmp->prev_sibling=0;
    return tmp;
    }

template <class T, class tree_node_allocator>
template <class iter>
iter tree<T, tree_node_allocator>::append_child(iter position, const T& x)
    {
    // If your program fails here you probably used 'append_child' to add the top
    // node to an empty tree. From version 1.45 the top element should be added
    // using 'insert'. See the documentation for further information, and sorry about
    // the API change.
    assert(position.node!=head);
    assert(position.node);

    tree_node* tmp = alloc_.allocate(1,0);
    kp::constructor(&tmp->data, x);
    tmp->first_child=0;
    tmp->last_child=0;

    tmp->parent=position.node;
    if(position.node->last_child!=0) {
        position.node->last_child->next_sibling=tmp;
        }
    else {
        position.node->first_child=tmp;
        }
    tmp->prev_sibling=position.node->last_child;
    position.node->last_child=tmp;
    tmp->next_sibling=0;
    return tmp;
    }

template <class T, class tree_node_allocator>
template <class iter>
iter tree<T, tree_node_allocator>::prepend_child(iter position, const T& x)
    {
    assert(position.node!=head);
    assert(position.node);

    tree_node* tmp = alloc_.allocate(1,0);
    kp::constructor(&tmp->data, x);
    tmp->first_child=0;
    tmp->last_child=0;

    tmp->parent=position.node;
    if(position.node->first_child!=0) {
        position.node->first_child->prev_sibling=tmp;
        }
    else {
        position.node->last_child=tmp;
        }
    tmp->next_sibling=position.node->first_child;
    position.node->first_child=tmp;
    tmp->prev_sibling=0;
    return tmp;
    }

template <class T, class tree_node_allocator>
template <class iter>
iter tree<T, tree_node_allocator>::append_child(iter position, iter other)
    {
    assert(position.node!=head);
    assert(position.node);

    sibling_iterator aargh=append_child(position, value_type());
    return replace(aargh, other);
    }

template <class T, class tree_node_allocator>
template <class iter>
iter tree<T, tree_node_allocator>::prepend_child(iter position, iter other)
    {
    assert(position.node!=head);
    assert(position.node);

    sibling_iterator aargh=prepend_child(position, value_type());
    return replace(aargh, other);
    }

template <class T, class tree_node_allocator>
template <class iter>
iter tree<T, tree_node_allocator>::append_children(iter position, sibling_iterator from, sibling_iterator to)
    {
    assert(position.node!=head);
    assert(position.node);

    iter ret=from;

    while(from!=to) {
        insert_subtree(position.end(), from);
        ++from;
        }
    return ret;
    }

template <class T, class tree_node_allocator>
template <class iter>
iter tree<T, tree_node_allocator>::prepend_children(iter position, sibling_iterator from, sibling_iterator to)
    {
    assert(position.node!=head);
    assert(position.node);

    iter ret=from;

    while(from!=to) {
        insert_subtree(position.begin(), from);
        ++from;
        }
    return ret;
    }

template <class T, class tree_node_allocator>
typename tree<T, tree_node_allocator>::pre_order_iterator tree<T, tree_node_allocator>::set_head(const T& x)
    {
    assert(head->next_sibling==feet);
    return insert(iterator(feet), x);
    }

template <class T, class tree_node_allocator>
template <class iter>
iter tree<T, tree_node_allocator>::insert(iter position, const T& x)
    {
    if(position.node==0) {
        position.node=feet; // Backward compatibility: when calling insert on a null node,
                            // insert before the feet.
        }
    tree_node* tmp = alloc_.allocate(1,0);
    kp::constructor(&tmp->data, x);
    tmp->first_child=0;
    tmp->last_child=0;

    tmp->parent=position.node->parent;
    tmp->next_sibling=position.node;
    tmp->prev_sibling=position.node->prev_sibling;
    position.node->prev_sibling=tmp;

    if(tmp->prev_sibling==0) {
        if(tmp->parent) // when inserting nodes at the head, there is no parent
            tmp->parent->first_child=tmp;
        }
    else
        tmp->prev_sibling->next_sibling=tmp;
    return tmp;
    }

template <class T, class tree_node_allocator>
typename tree<T, tree_node_allocator>::sibling_iterator tree<T, tree_node_allocator>::insert(sibling_iterator position, const T& x)
    {
    tree_node* tmp = alloc_.allocate(1,0);
    kp::constructor(&tmp->data, x);
    tmp->first_child=0;
    tmp->last_child=0;

    tmp->next_sibling=position.node;
    if(position.node==0) { // iterator points to end of a subtree
        tmp->parent=position.parent_;
        tmp->prev_sibling=position.range_last();
        tmp->parent->last_child=tmp;
        }
    else {
        tmp->parent=position.node->parent;
        tmp->prev_sibling=position.node->prev_sibling;
        position.node->prev_sibling=tmp;
        }

    if(tmp->prev_sibling==0) {
        if(tmp->parent) // when inserting nodes at the head, there is no parent
            tmp->parent->first_child=tmp;
        }
    else
        tmp->prev_sibling->next_sibling=tmp;
    return tmp;
    }

template <class T, class tree_node_allocator>
template <class iter>
iter tree<T, tree_node_allocator>::insert_after(iter position, const T& x)
    {
    tree_node* tmp = alloc_.allocate(1,0);
    kp::constructor(&tmp->data, x);
    tmp->first_child=0;
    tmp->last_child=0;

    tmp->parent=position.node->parent;
    tmp->prev_sibling=position.node;
    tmp->next_sibling=position.node->next_sibling;
    position.node->next_sibling=tmp;

    if(tmp->next_sibling==0) {
        if(tmp->parent) // when inserting nodes at the head, there is no parent
            tmp->parent->last_child=tmp;
        }
    else {
        tmp->next_sibling->prev_sibling=tmp;
        }
    return tmp;
    }

template <class T, class tree_node_allocator>
template <class iter>
iter tree<T, tree_node_allocator>::insert_subtree(iter position, const iterator_base& subtree)
    {
    // insert dummy
    iter it=insert(position, value_type());
    // replace dummy with subtree
    return replace(it, subtree);
    }

template <class T, class tree_node_allocator>
template <class iter>
iter tree<T, tree_node_allocator>::insert_subtree_after(iter position, const iterator_base& subtree)
    {
    // insert dummy
    iter it=insert_after(position, value_type());
    // replace dummy with subtree
    return replace(it, subtree);
    }

// template <class T, class tree_node_allocator>
// template <class iter>
// iter tree<T, tree_node_allocator>::insert_subtree(sibling_iterator position, iter subtree)
//  {
//  // insert dummy
//  iter it(insert(position, value_type()));
//  // replace dummy with subtree
//  return replace(it, subtree);
//  }

template <class T, class tree_node_allocator>
template <class iter>
iter tree<T, tree_node_allocator>::replace(iter position, const T& x)
    {
    kp::destructor(&position.node->data);
    kp::constructor(&position.node->data, x);
    return position;
    }

template <class T, class tree_node_allocator>
template <class iter>
iter tree<T, tree_node_allocator>::replace(iter position, const iterator_base& from)
    {
    assert(position.node!=head);
    tree_node *current_from=from.node;
    tree_node *start_from=from.node;
    tree_node *current_to  =position.node;

    // replace the node at position with head of the replacement tree at from
//  std::cout << "warning!" << position.node << std::endl;
    erase_children(position);   
//  std::cout << "no warning!" << std::endl;
    tree_node* tmp = alloc_.allocate(1,0);
    kp::constructor(&tmp->data, (*from));
    tmp->first_child=0;
    tmp->last_child=0;
    if(current_to->prev_sibling==0) {
        if(current_to->parent!=0)
            current_to->parent->first_child=tmp;
        }
    else {
        current_to->prev_sibling->next_sibling=tmp;
        }
    tmp->prev_sibling=current_to->prev_sibling;
    if(current_to->next_sibling==0) {
        if(current_to->parent!=0)
            current_to->parent->last_child=tmp;
        }
    else {
        current_to->next_sibling->prev_sibling=tmp;
        }
    tmp->next_sibling=current_to->next_sibling;
    tmp->parent=current_to->parent;
    kp::destructor(&current_to->data);
    alloc_.deallocate(current_to,1);
    current_to=tmp;
    
    // only at this stage can we fix 'last'
    tree_node *last=from.node->next_sibling;

    pre_order_iterator toit=tmp;
    // copy all children
    do {
        assert(current_from!=0);
        if(current_from->first_child != 0) {
            current_from=current_from->first_child;
            toit=append_child(toit, current_from->data);
            }
        else {
            while(current_from->next_sibling==0 && current_from!=start_from) {
                current_from=current_from->parent;
                toit=parent(toit);
                assert(current_from!=0);
                }
            current_from=current_from->next_sibling;
            if(current_from!=last) {
                toit=append_child(parent(toit), current_from->data);
                }
            }
        } while(current_from!=last);

    return current_to;
    }

template <class T, class tree_node_allocator>
typename tree<T, tree_node_allocator>::sibling_iterator tree<T, tree_node_allocator>::replace(
    sibling_iterator orig_begin, 
    sibling_iterator orig_end, 
    sibling_iterator new_begin, 
    sibling_iterator new_end)
    {
    tree_node *orig_first=orig_begin.node;
    tree_node *new_first=new_begin.node;
    tree_node *orig_last=orig_first;
    while((++orig_begin)!=orig_end)
        orig_last=orig_last->next_sibling;
    tree_node *new_last=new_first;
    while((++new_begin)!=new_end)
        new_last=new_last->next_sibling;

    // insert all siblings in new_first..new_last before orig_first
    bool first=true;
    pre_order_iterator ret;
    while(1==1) {
        pre_order_iterator tt=insert_subtree(pre_order_iterator(orig_first), pre_order_iterator(new_first));
        if(first) {
            ret=tt;
            first=false;
            }
        if(new_first==new_last)
            break;
        new_first=new_first->next_sibling;
        }

    // erase old range of siblings
    bool last=false;
    tree_node *next=orig_first;
    while(1==1) {
        if(next==orig_last) 
            last=true;
        next=next->next_sibling;
        erase((pre_order_iterator)orig_first);
        if(last) 
            break;
        orig_first=next;
        }
    return ret;
    }

template <class T, class tree_node_allocator>
template <typename iter>
iter tree<T, tree_node_allocator>::flatten(iter position)
    {
    if(position.node->first_child==0)
        return position;

    tree_node *tmp=position.node->first_child;
    while(tmp) {
        tmp->parent=position.node->parent;
        tmp=tmp->next_sibling;
        } 
    if(position.node->next_sibling) {
        position.node->last_child->next_sibling=position.node->next_sibling;
        position.node->next_sibling->prev_sibling=position.node->last_child;
        }
    else {
        position.node->parent->last_child=position.node->last_child;
        }
    position.node->next_sibling=position.node->first_child;
    position.node->next_sibling->prev_sibling=position.node;
    position.node->first_child=0;
    position.node->last_child=0;

    return position;
    }


template <class T, class tree_node_allocator>
template <typename iter>
iter tree<T, tree_node_allocator>::reparent(iter position, sibling_iterator begin, sibling_iterator end)
    {
    tree_node *first=begin.node;
    tree_node *last=first;

    assert(first!=position.node);
    
    if(begin==end) return begin;
    // determine last node
    while((++begin)!=end) {
        last=last->next_sibling;
        }
    // move subtree
    if(first->prev_sibling==0) {
        first->parent->first_child=last->next_sibling;
        }
    else {
        first->prev_sibling->next_sibling=last->next_sibling;
        }
    if(last->next_sibling==0) {
        last->parent->last_child=first->prev_sibling;
        }
    else {
        last->next_sibling->prev_sibling=first->prev_sibling;
        }
    if(position.node->first_child==0) {
        position.node->first_child=first;
        position.node->last_child=last;
        first->prev_sibling=0;
        }
    else {
        position.node->last_child->next_sibling=first;
        first->prev_sibling=position.node->last_child;
        position.node->last_child=last;
        }
    last->next_sibling=0;

    tree_node *pos=first;
   for(;;) {
        pos->parent=position.node;
        if(pos==last) break;
        pos=pos->next_sibling;
        }

    return first;
    }

template <class T, class tree_node_allocator>
template <typename iter> iter tree<T, tree_node_allocator>::reparent(iter position, iter from)
    {
    if(from.node->first_child==0) return position;
    return reparent(position, from.node->first_child, end(from));
    }

template <class T, class tree_node_allocator>
template <typename iter> iter tree<T, tree_node_allocator>::wrap(iter position, const T& x)
    {
    assert(position.node!=0);
    sibling_iterator fr=position, to=position;
    ++to;
    iter ret = insert(position, x);
    reparent(ret, fr, to);
    return ret;
    }

template <class T, class tree_node_allocator>
template <typename iter> iter tree<T, tree_node_allocator>::move_after(iter target, iter source)
   {
   tree_node *dst=target.node;
   tree_node *src=source.node;
   assert(dst);
   assert(src);

   if(dst==src) return source;
    if(dst->next_sibling)
        if(dst->next_sibling==src) // already in the right spot
            return source;

   // take src out of the tree
   if(src->prev_sibling!=0) src->prev_sibling->next_sibling=src->next_sibling;
   else                     src->parent->first_child=src->next_sibling;
   if(src->next_sibling!=0) src->next_sibling->prev_sibling=src->prev_sibling;
   else                     src->parent->last_child=src->prev_sibling;

   // connect it to the new point
   if(dst->next_sibling!=0) dst->next_sibling->prev_sibling=src;
   else                     dst->parent->last_child=src;
   src->next_sibling=dst->next_sibling;
   dst->next_sibling=src;
   src->prev_sibling=dst;
   src->parent=dst->parent;
   return src;
   }

template <class T, class tree_node_allocator>
template <typename iter> iter tree<T, tree_node_allocator>::move_before(iter target, iter source)
   {
   tree_node *dst=target.node;
   tree_node *src=source.node;
   assert(dst);
   assert(src);

   if(dst==src) return source;
    if(dst->prev_sibling)
        if(dst->prev_sibling==src) // already in the right spot
            return source;

   // take src out of the tree
   if(src->prev_sibling!=0) src->prev_sibling->next_sibling=src->next_sibling;
   else                     src->parent->first_child=src->next_sibling;
   if(src->next_sibling!=0) src->next_sibling->prev_sibling=src->prev_sibling;
   else                     src->parent->last_child=src->prev_sibling;

   // connect it to the new point
   if(dst->prev_sibling!=0) dst->prev_sibling->next_sibling=src;
   else                     dst->parent->first_child=src;
   src->prev_sibling=dst->prev_sibling;
   dst->prev_sibling=src;
   src->next_sibling=dst;
   src->parent=dst->parent;
   return src;
   }

// specialisation for sibling_iterators
template <class T, class tree_node_allocator>
typename tree<T, tree_node_allocator>::sibling_iterator tree<T, tree_node_allocator>::move_before(sibling_iterator target, 
                                                                                                                      sibling_iterator source)
    {
    tree_node *dst=target.node;
    tree_node *src=source.node;
    tree_node *dst_prev_sibling;
    if(dst==0) { // must then be an end iterator
        dst_prev_sibling=target.parent_->last_child;
        assert(dst_prev_sibling);
        }
    else dst_prev_sibling=dst->prev_sibling;
    assert(src);

    if(dst==src) return source;
    if(dst_prev_sibling)
        if(dst_prev_sibling==src) // already in the right spot
            return source;

    // take src out of the tree
    if(src->prev_sibling!=0) src->prev_sibling->next_sibling=src->next_sibling;
    else                     src->parent->first_child=src->next_sibling;
    if(src->next_sibling!=0) src->next_sibling->prev_sibling=src->prev_sibling;
    else                     src->parent->last_child=src->prev_sibling;

    // connect it to the new point
    if(dst_prev_sibling!=0) dst_prev_sibling->next_sibling=src;
    else                    target.parent_->first_child=src;
    src->prev_sibling=dst_prev_sibling;
    if(dst) {
        dst->prev_sibling=src;
        src->parent=dst->parent;
        }
    src->next_sibling=dst;
    return src;
    }

template <class T, class tree_node_allocator>
template <typename iter> iter tree<T, tree_node_allocator>::move_ontop(iter target, iter source)
    {
    tree_node *dst=target.node;
    tree_node *src=source.node;
    assert(dst);
    assert(src);

    if(dst==src) return source;

    // remember connection points
    tree_node *b_prev_sibling=dst->prev_sibling;
    tree_node *b_next_sibling=dst->next_sibling;
    tree_node *b_parent=dst->parent;

    // remove target
    erase(target);

    // take src out of the tree
    if(src->prev_sibling!=0) src->prev_sibling->next_sibling=src->next_sibling;
    else                     src->parent->first_child=src->next_sibling;
    if(src->next_sibling!=0) src->next_sibling->prev_sibling=src->prev_sibling;
    else                     src->parent->last_child=src->prev_sibling;

    // connect it to the new point
    if(b_prev_sibling!=0) b_prev_sibling->next_sibling=src;
    else                  b_parent->first_child=src;
    if(b_next_sibling!=0) b_next_sibling->prev_sibling=src;
    else                  b_parent->last_child=src;
    src->prev_sibling=b_prev_sibling;
    src->next_sibling=b_next_sibling;
    src->parent=b_parent;
    return src;
    }

template <class T, class tree_node_allocator>
void tree<T, tree_node_allocator>::merge(sibling_iterator to1,   sibling_iterator to2,
                                                        sibling_iterator from1, sibling_iterator from2,
                                                        bool duplicate_leaves)
    {
    sibling_iterator fnd;
    while(from1!=from2) {
        if((fnd=std::find(to1, to2, (*from1))) != to2) { // element found
            if(from1.begin()==from1.end()) { // full depth reached
                if(duplicate_leaves)
                    append_child(parent(to1), (*from1));
                }
            else { // descend further
                merge(fnd.begin(), fnd.end(), from1.begin(), from1.end(), duplicate_leaves);
                }
            }
        else { // element missing
            insert_subtree(to2, from1);
            }
        ++from1;
        }
    }


template <class T, class tree_node_allocator>
void tree<T, tree_node_allocator>::sort(sibling_iterator from, sibling_iterator to, bool deep)
    {
    std::less<T> comp;
    sort(from, to, comp, deep);
    }

template <class T, class tree_node_allocator>
template <class StrictWeakOrdering>
void tree<T, tree_node_allocator>::sort(sibling_iterator from, sibling_iterator to, 
                                                     StrictWeakOrdering comp, bool deep)
    {
    if(from==to) return;
    // make list of sorted nodes
    // CHECK: if multiset stores equivalent nodes in the order in which they
    // are inserted, then this routine should be called 'stable_sort'.
    std::multiset<tree_node *, compare_nodes<StrictWeakOrdering> > nodes(comp);
    sibling_iterator it=from, it2=to;
    while(it != to) {
        nodes.insert(it.node);
        ++it;
        }
    // reassemble
    --it2;

    // prev and next are the nodes before and after the sorted range
    tree_node *prev=from.node->prev_sibling;
    tree_node *next=it2.node->next_sibling;
    typename std::multiset<tree_node *, compare_nodes<StrictWeakOrdering> >::iterator nit=nodes.begin(), eit=nodes.end();
    if(prev==0) {
        if((*nit)->parent!=0) // to catch "sorting the head" situations, when there is no parent
            (*nit)->parent->first_child=(*nit);
        }
    else prev->next_sibling=(*nit);

    --eit;
    while(nit!=eit) {
        (*nit)->prev_sibling=prev;
        if(prev)
            prev->next_sibling=(*nit);
        prev=(*nit);
        ++nit;
        }
    // prev now points to the last-but-one node in the sorted range
    if(prev)
        prev->next_sibling=(*eit);

    // eit points to the last node in the sorted range.
    (*eit)->next_sibling=next;
   (*eit)->prev_sibling=prev; // missed in the loop above
    if(next==0) {
        if((*eit)->parent!=0) // to catch "sorting the head" situations, when there is no parent
            (*eit)->parent->last_child=(*eit);
        }
    else next->prev_sibling=(*eit);

    if(deep) {  // sort the children of each node too
        sibling_iterator bcs(*nodes.begin());
        sibling_iterator ecs(*eit);
        ++ecs;
        while(bcs!=ecs) {
            sort(begin(bcs), end(bcs), comp, deep);
            ++bcs;
            }
        }
    }

template <class T, class tree_node_allocator>
template <typename iter>
bool tree<T, tree_node_allocator>::equal(const iter& one_, const iter& two, const iter& three_) const
    {
    std::equal_to<T> comp;
    return equal(one_, two, three_, comp);
    }

template <class T, class tree_node_allocator>
template <typename iter>
bool tree<T, tree_node_allocator>::equal_subtree(const iter& one_, const iter& two_) const
    {
    std::equal_to<T> comp;
    return equal_subtree(one_, two_, comp);
    }

template <class T, class tree_node_allocator>
template <typename iter, class BinaryPredicate>
bool tree<T, tree_node_allocator>::equal(const iter& one_, const iter& two, const iter& three_, BinaryPredicate fun) const
    {
    pre_order_iterator one(one_), three(three_);

//  if(one==two && is_valid(three) && three.number_of_children()!=0)
//      return false;
    while(one!=two && is_valid(three)) {
        if(!fun(*one,*three))
            return false;
        if(one.number_of_children()!=three.number_of_children()) 
            return false;
        ++one;
        ++three;
        }
    return true;
    }

template <class T, class tree_node_allocator>
template <typename iter, class BinaryPredicate>
bool tree<T, tree_node_allocator>::equal_subtree(const iter& one_, const iter& two_, BinaryPredicate fun) const
    {
    pre_order_iterator one(one_), two(two_);

    if(!fun(*one,*two)) return false;
    if(number_of_children(one)!=number_of_children(two)) return false;
    return equal(begin(one),end(one),begin(two),fun);
    }

template <class T, class tree_node_allocator>
tree<T, tree_node_allocator> tree<T, tree_node_allocator>::subtree(sibling_iterator from, sibling_iterator to) const
    {
    tree tmp;
    tmp.set_head(value_type());
    tmp.replace(tmp.begin(), tmp.end(), from, to);
    return tmp;
    }

template <class T, class tree_node_allocator>
void tree<T, tree_node_allocator>::subtree(tree& tmp, sibling_iterator from, sibling_iterator to) const
    {
    tmp.set_head(value_type());
    tmp.replace(tmp.begin(), tmp.end(), from, to);
    }

template <class T, class tree_node_allocator>
size_t tree<T, tree_node_allocator>::size() const
    {
    size_t i=0;
    pre_order_iterator it=begin(), eit=end();
    while(it!=eit) {
        ++i;
        ++it;
        }
    return i;
    }

template <class T, class tree_node_allocator>
size_t tree<T, tree_node_allocator>::size(const iterator_base& top) const
    {
    size_t i=0;
    pre_order_iterator it=top, eit=top;
    eit.skip_children();
    ++eit;
    while(it!=eit) {
        ++i;
        ++it;
        }
    return i;
    }

template <class T, class tree_node_allocator>
bool tree<T, tree_node_allocator>::empty() const
    {
    pre_order_iterator it=begin(), eit=end();
    return (it==eit);
    }

template <class T, class tree_node_allocator>
int tree<T, tree_node_allocator>::depth(const iterator_base& it) 
    {
    tree_node* pos=it.node;
    assert(pos!=0);
    int ret=0;
    while(pos->parent!=0) {
        pos=pos->parent;
        ++ret;
        }
    return ret;
    }

template <class T, class tree_node_allocator>
int tree<T, tree_node_allocator>::depth(const iterator_base& it, const iterator_base& root) 
    {
    tree_node* pos=it.node;
    assert(pos!=0);
    int ret=0;
    while(pos->parent!=0 && pos!=root.node) {
        pos=pos->parent;
        ++ret;
        }
    return ret;
    }

template <class T, class tree_node_allocator>
int tree<T, tree_node_allocator>::max_depth() const
    {
    int maxd=-1;
    for(tree_node *it = head->next_sibling; it!=feet; it=it->next_sibling)
        maxd=std::max(maxd, max_depth(it));

    return maxd;
    }


template <class T, class tree_node_allocator>
int tree<T, tree_node_allocator>::max_depth(const iterator_base& pos) const
    {
    tree_node *tmp=pos.node;

    if(tmp==0 || tmp==head || tmp==feet) return -1;

    int curdepth=0, maxdepth=0;
    while(true) { // try to walk the bottom of the tree
        while(tmp->first_child==0) {
            if(tmp==pos.node) return maxdepth;
            if(tmp->next_sibling==0) {
                // try to walk up and then right again
                do {
                    tmp=tmp->parent;
               if(tmp==0) return maxdepth;
               --curdepth;
                   } while(tmp->next_sibling==0);
                }
         if(tmp==pos.node) return maxdepth;
            tmp=tmp->next_sibling;
            }
        tmp=tmp->first_child;
        ++curdepth;
        maxdepth=std::max(curdepth, maxdepth);
        } 
    }

template <class T, class tree_node_allocator>
unsigned int tree<T, tree_node_allocator>::number_of_children(const iterator_base& it) 
    {
    tree_node *pos=it.node->first_child;
    if(pos==0) return 0;
    
    unsigned int ret=1;
//    while(pos!=it.node->last_child) {
//        ++ret;
//        pos=pos->next_sibling;
//        }
    while((pos=pos->next_sibling))
        ++ret;
    return ret;
    }

template <class T, class tree_node_allocator>
unsigned int tree<T, tree_node_allocator>::number_of_siblings(const iterator_base& it) const
    {
    tree_node *pos=it.node;
    unsigned int ret=0;
    // count forward
    while(pos->next_sibling && 
            pos->next_sibling!=head &&
            pos->next_sibling!=feet) {
        ++ret;
        pos=pos->next_sibling;
        }
    // count backward
    pos=it.node;
    while(pos->prev_sibling && 
            pos->prev_sibling!=head &&
            pos->prev_sibling!=feet) {
        ++ret;
        pos=pos->prev_sibling;
        }
    
    return ret;
    }

template <class T, class tree_node_allocator>
void tree<T, tree_node_allocator>::swap(sibling_iterator it)
    {
    tree_node *nxt=it.node->next_sibling;
    if(nxt) {
        if(it.node->prev_sibling)
            it.node->prev_sibling->next_sibling=nxt;
        else
            it.node->parent->first_child=nxt;
        nxt->prev_sibling=it.node->prev_sibling;
        tree_node *nxtnxt=nxt->next_sibling;
        if(nxtnxt)
            nxtnxt->prev_sibling=it.node;
        else
            it.node->parent->last_child=it.node;
        nxt->next_sibling=it.node;
        it.node->prev_sibling=nxt;
        it.node->next_sibling=nxtnxt;
        }
    }

template <class T, class tree_node_allocator>
void tree<T, tree_node_allocator>::swap(iterator one, iterator two)
    {
    // if one and two are adjacent siblings, use the sibling swap
    if(one.node->next_sibling==two.node) swap(one);
    else if(two.node->next_sibling==one.node) swap(two);
    else {
        tree_node *nxt1=one.node->next_sibling;
        tree_node *nxt2=two.node->next_sibling;
        tree_node *pre1=one.node->prev_sibling;
        tree_node *pre2=two.node->prev_sibling;
        tree_node *par1=one.node->parent;
        tree_node *par2=two.node->parent;

        // reconnect
        one.node->parent=par2;
        one.node->next_sibling=nxt2;
        if(nxt2) nxt2->prev_sibling=one.node;
        else     par2->last_child=one.node;
        one.node->prev_sibling=pre2;
        if(pre2) pre2->next_sibling=one.node;
        else     par2->first_child=one.node;    

        two.node->parent=par1;
        two.node->next_sibling=nxt1;
        if(nxt1) nxt1->prev_sibling=two.node;
        else     par1->last_child=two.node;
        two.node->prev_sibling=pre1;
        if(pre1) pre1->next_sibling=two.node;
        else     par1->first_child=two.node;
        }
    }

// template <class BinaryPredicate>
// tree<T, tree_node_allocator>::iterator tree<T, tree_node_allocator>::find_subtree(
//  sibling_iterator subfrom, sibling_iterator subto, iterator from, iterator to, 
//  BinaryPredicate fun) const
//  {
//  assert(1==0); // this routine is not finished yet.
//  while(from!=to) {
//      if(fun(*subfrom, *from)) {
//          
//          }
//      }
//  return to;
//  }

template <class T, class tree_node_allocator>
bool tree<T, tree_node_allocator>::is_in_subtree(const iterator_base& it, const iterator_base& begin, 
                                                                 const iterator_base& end) const
    {
    // FIXME: this should be optimised.
    pre_order_iterator tmp=begin;
    while(tmp!=end) {
        if(tmp==it) return true;
        ++tmp;
        }
    return false;
    }

template <class T, class tree_node_allocator>
bool tree<T, tree_node_allocator>::is_valid(const iterator_base& it) const
    {
    if(it.node==0 || it.node==feet || it.node==head) return false;
    else return true;
    }

template <class T, class tree_node_allocator>
unsigned int tree<T, tree_node_allocator>::index(sibling_iterator it) const
    {
    unsigned int ind=0;
    if(it.node->parent==0) {
        while(it.node->prev_sibling!=head) {
            it.node=it.node->prev_sibling;
            ++ind;
            }
        }
    else {
        while(it.node->prev_sibling!=0) {
            it.node=it.node->prev_sibling;
            ++ind;
            }
        }
    return ind;
    }

template <class T, class tree_node_allocator>
typename tree<T, tree_node_allocator>::sibling_iterator tree<T, tree_node_allocator>::sibling(const iterator_base& it, unsigned int num)
   {
   tree_node *tmp;
   if(it.node->parent==0) {
      tmp=head->next_sibling;
      while(num) {
         tmp = tmp->next_sibling;
         --num;
         }
      }
   else {
      tmp=it.node->parent->first_child;
      while(num) {
         assert(tmp!=0);
         tmp = tmp->next_sibling;
         --num;
         }
      }
   return tmp;
   }
 

template <class T, class tree_node_allocator>
typename tree<T, tree_node_allocator>::sibling_iterator tree<T, tree_node_allocator>::child(const iterator_base& it, unsigned int num) 
    {
    tree_node *tmp=it.node->first_child;
    while(num--) {
        assert(tmp!=0);
        tmp=tmp->next_sibling;
        }
    return tmp;
    }




// Iterator base

template <class T, class tree_node_allocator>
tree<T, tree_node_allocator>::iterator_base::iterator_base()
    : node(0), skip_current_children_(false)
    {
    }

template <class T, class tree_node_allocator>
tree<T, tree_node_allocator>::iterator_base::iterator_base(tree_node *tn)
    : node(tn), skip_current_children_(false)
    {
    }

template <class T, class tree_node_allocator>
T& tree<T, tree_node_allocator>::iterator_base::operator*() const
    {
    return node->data;
    }

template <class T, class tree_node_allocator>
T* tree<T, tree_node_allocator>::iterator_base::operator->() const
    {
    return &(node->data);
    }

template <class T, class tree_node_allocator>
bool tree<T, tree_node_allocator>::post_order_iterator::operator!=(const post_order_iterator& other) const
    {
    if(other.node!=this->node) return true;
    else return false;
    }

template <class T, class tree_node_allocator>
bool tree<T, tree_node_allocator>::post_order_iterator::operator==(const post_order_iterator& other) const
    {
    if(other.node==this->node) return true;
    else return false;
    }

template <class T, class tree_node_allocator>
bool tree<T, tree_node_allocator>::pre_order_iterator::operator!=(const pre_order_iterator& other) const
    {
    if(other.node!=this->node) return true;
    else return false;
    }

template <class T, class tree_node_allocator>
bool tree<T, tree_node_allocator>::pre_order_iterator::operator==(const pre_order_iterator& other) const
    {
    if(other.node==this->node) return true;
    else return false;
    }

template <class T, class tree_node_allocator>
bool tree<T, tree_node_allocator>::sibling_iterator::operator!=(const sibling_iterator& other) const
    {
    if(other.node!=this->node) return true;
    else return false;
    }

template <class T, class tree_node_allocator>
bool tree<T, tree_node_allocator>::sibling_iterator::operator==(const sibling_iterator& other) const
    {
    if(other.node==this->node) return true;
    else return false;
    }

template <class T, class tree_node_allocator>
bool tree<T, tree_node_allocator>::leaf_iterator::operator!=(const leaf_iterator& other) const
   {
   if(other.node!=this->node) return true;
   else return false;
   }

template <class T, class tree_node_allocator>
bool tree<T, tree_node_allocator>::leaf_iterator::operator==(const leaf_iterator& other) const
   {
   if(other.node==this->node && other.top_node==this->top_node) return true;
   else return false;
   }

template <class T, class tree_node_allocator>
typename tree<T, tree_node_allocator>::sibling_iterator tree<T, tree_node_allocator>::iterator_base::begin() const
    {
    if(node->first_child==0) 
        return end();

    sibling_iterator ret(node->first_child);
    ret.parent_=this->node;
    return ret;
    }

template <class T, class tree_node_allocator>
typename tree<T, tree_node_allocator>::sibling_iterator tree<T, tree_node_allocator>::iterator_base::end() const
    {
    sibling_iterator ret(0);
    ret.parent_=node;
    return ret;
    }

template <class T, class tree_node_allocator>
void tree<T, tree_node_allocator>::iterator_base::skip_children()
    {
    skip_current_children_=true;
    }

template <class T, class tree_node_allocator>
void tree<T, tree_node_allocator>::iterator_base::skip_children(bool skip)
   {
   skip_current_children_=skip;
   }

template <class T, class tree_node_allocator>
unsigned int tree<T, tree_node_allocator>::iterator_base::number_of_children() const
    {
    tree_node *pos=node->first_child;
    if(pos==0) return 0;
    
    unsigned int ret=1;
    while(pos!=node->last_child) {
        ++ret;
        pos=pos->next_sibling;
        }
    return ret;
    }



// Pre-order iterator

template <class T, class tree_node_allocator>
tree<T, tree_node_allocator>::pre_order_iterator::pre_order_iterator() 
    : iterator_base(0)
    {
    }

template <class T, class tree_node_allocator>
tree<T, tree_node_allocator>::pre_order_iterator::pre_order_iterator(tree_node *tn)
    : iterator_base(tn)
    {
    }

template <class T, class tree_node_allocator>
tree<T, tree_node_allocator>::pre_order_iterator::pre_order_iterator(const iterator_base &other)
    : iterator_base(other.node)
    {
    }

template <class T, class tree_node_allocator>
tree<T, tree_node_allocator>::pre_order_iterator::pre_order_iterator(const sibling_iterator& other)
    : iterator_base(other.node)
    {
    if(this->node==0) {
        if(other.range_last()!=0)
            this->node=other.range_last();
        else 
            this->node=other.parent_;
        this->skip_children();
        ++(*this);
        }
    }

template <class T, class tree_node_allocator>
typename tree<T, tree_node_allocator>::pre_order_iterator& tree<T, tree_node_allocator>::pre_order_iterator::operator++()
    {
    assert(this->node!=0);
    if(!this->skip_current_children_ && this->node->first_child != 0) {
        this->node=this->node->first_child;
        }
    else {
        this->skip_current_children_=false;
        while(this->node->next_sibling==0) {
            this->node=this->node->parent;
            if(this->node==0)
                return *this;
            }
        this->node=this->node->next_sibling;
        }
    return *this;
    }

template <class T, class tree_node_allocator>
typename tree<T, tree_node_allocator>::pre_order_iterator& tree<T, tree_node_allocator>::pre_order_iterator::operator--()
    {
    assert(this->node!=0);
    if(this->node->prev_sibling) {
        this->node=this->node->prev_sibling;
        while(this->node->last_child)
            this->node=this->node->last_child;
        }
    else {
        this->node=this->node->parent;
        if(this->node==0)
            return *this;
        }
    return *this;
}

template <class T, class tree_node_allocator>
typename tree<T, tree_node_allocator>::pre_order_iterator tree<T, tree_node_allocator>::pre_order_iterator::operator++(int)
    {
    pre_order_iterator copy = *this;
    ++(*this);
    return copy;
    }

template <class T, class tree_node_allocator>
typename tree<T, tree_node_allocator>::pre_order_iterator tree<T, tree_node_allocator>::pre_order_iterator::operator--(int)
{
  pre_order_iterator copy = *this;
  --(*this);
  return copy;
}

template <class T, class tree_node_allocator>
typename tree<T, tree_node_allocator>::pre_order_iterator& tree<T, tree_node_allocator>::pre_order_iterator::operator+=(unsigned int num)
    {
    while(num>0) {
        ++(*this);
        --num;
        }
    return (*this);
    }

template <class T, class tree_node_allocator>
typename tree<T, tree_node_allocator>::pre_order_iterator& tree<T, tree_node_allocator>::pre_order_iterator::operator-=(unsigned int num)
    {
    while(num>0) {
        --(*this);
        --num;
        }
    return (*this);
    }



// Post-order iterator

template <class T, class tree_node_allocator>
tree<T, tree_node_allocator>::post_order_iterator::post_order_iterator() 
    : iterator_base(0)
    {
    }

template <class T, class tree_node_allocator>
tree<T, tree_node_allocator>::post_order_iterator::post_order_iterator(tree_node *tn)
    : iterator_base(tn)
    {
    }

template <class T, class tree_node_allocator>
tree<T, tree_node_allocator>::post_order_iterator::post_order_iterator(const iterator_base &other)
    : iterator_base(other.node)
    {
    }

template <class T, class tree_node_allocator>
tree<T, tree_node_allocator>::post_order_iterator::post_order_iterator(const sibling_iterator& other)
    : iterator_base(other.node)
    {
    if(this->node==0) {
        if(other.range_last()!=0)
            this->node=other.range_last();
        else 
            this->node=other.parent_;
        this->skip_children();
        ++(*this);
        }
    }

template <class T, class tree_node_allocator>
typename tree<T, tree_node_allocator>::post_order_iterator& tree<T, tree_node_allocator>::post_order_iterator::operator++()
    {
    assert(this->node!=0);
    if(this->node->next_sibling==0) {
        this->node=this->node->parent;
        this->skip_current_children_=false;
        }
    else {
        this->node=this->node->next_sibling;
        if(this->skip_current_children_) {
            this->skip_current_children_=false;
            }
        else {
            while(this->node->first_child)
                this->node=this->node->first_child;
            }
        }
    return *this;
    }

template <class T, class tree_node_allocator>
typename tree<T, tree_node_allocator>::post_order_iterator& tree<T, tree_node_allocator>::post_order_iterator::operator--()
    {
    assert(this->node!=0);
    if(this->skip_current_children_ || this->node->last_child==0) {
        this->skip_current_children_=false;
        while(this->node->prev_sibling==0)
            this->node=this->node->parent;
        this->node=this->node->prev_sibling;
        }
    else {
        this->node=this->node->last_child;
        }
    return *this;
    }

template <class T, class tree_node_allocator>
typename tree<T, tree_node_allocator>::post_order_iterator tree<T, tree_node_allocator>::post_order_iterator::operator++(int)
    {
    post_order_iterator copy = *this;
    ++(*this);
    return copy;
    }

template <class T, class tree_node_allocator>
typename tree<T, tree_node_allocator>::post_order_iterator tree<T, tree_node_allocator>::post_order_iterator::operator--(int)
    {
    post_order_iterator copy = *this;
    --(*this);
    return copy;
    }


template <class T, class tree_node_allocator>
typename tree<T, tree_node_allocator>::post_order_iterator& tree<T, tree_node_allocator>::post_order_iterator::operator+=(unsigned int num)
    {
    while(num>0) {
        ++(*this);
        --num;
        }
    return (*this);
    }

template <class T, class tree_node_allocator>
typename tree<T, tree_node_allocator>::post_order_iterator& tree<T, tree_node_allocator>::post_order_iterator::operator-=(unsigned int num)
    {
    while(num>0) {
        --(*this);
        --num;
        }
    return (*this);
    }

template <class T, class tree_node_allocator>
void tree<T, tree_node_allocator>::post_order_iterator::descend_all()
    {
    assert(this->node!=0);
    while(this->node->first_child)
        this->node=this->node->first_child;
    }


// Breadth-first iterator

template <class T, class tree_node_allocator>
tree<T, tree_node_allocator>::breadth_first_queued_iterator::breadth_first_queued_iterator()
    : iterator_base()
    {
    }

template <class T, class tree_node_allocator>
tree<T, tree_node_allocator>::breadth_first_queued_iterator::breadth_first_queued_iterator(tree_node *tn)
    : iterator_base(tn)
    {
    traversal_queue.push(tn);
    }

template <class T, class tree_node_allocator>
tree<T, tree_node_allocator>::breadth_first_queued_iterator::breadth_first_queued_iterator(const iterator_base& other)
    : iterator_base(other.node)
    {
    traversal_queue.push(other.node);
    }

template <class T, class tree_node_allocator>
bool tree<T, tree_node_allocator>::breadth_first_queued_iterator::operator!=(const breadth_first_queued_iterator& other) const
    {
    if(other.node!=this->node) return true;
    else return false;
    }

template <class T, class tree_node_allocator>
bool tree<T, tree_node_allocator>::breadth_first_queued_iterator::operator==(const breadth_first_queued_iterator& other) const
    {
    if(other.node==this->node) return true;
    else return false;
    }

template <class T, class tree_node_allocator>
typename tree<T, tree_node_allocator>::breadth_first_queued_iterator& tree<T, tree_node_allocator>::breadth_first_queued_iterator::operator++()
    {
    assert(this->node!=0);

    // Add child nodes and pop current node
    sibling_iterator sib=this->begin();
    while(sib!=this->end()) {
        traversal_queue.push(sib.node);
        ++sib;
        }
    traversal_queue.pop();
    if(traversal_queue.size()>0)
        this->node=traversal_queue.front();
    else 
        this->node=0;
    return (*this);
    }

template <class T, class tree_node_allocator>
typename tree<T, tree_node_allocator>::breadth_first_queued_iterator tree<T, tree_node_allocator>::breadth_first_queued_iterator::operator++(int)
    {
    breadth_first_queued_iterator copy = *this;
    ++(*this);
    return copy;
    }

template <class T, class tree_node_allocator>
typename tree<T, tree_node_allocator>::breadth_first_queued_iterator& tree<T, tree_node_allocator>::breadth_first_queued_iterator::operator+=(unsigned int num)
    {
    while(num>0) {
        ++(*this);
        --num;
        }
    return (*this);
    }



// Fixed depth iterator

template <class T, class tree_node_allocator>
tree<T, tree_node_allocator>::fixed_depth_iterator::fixed_depth_iterator()
    : iterator_base()
    {
    }

template <class T, class tree_node_allocator>
tree<T, tree_node_allocator>::fixed_depth_iterator::fixed_depth_iterator(tree_node *tn)
    : iterator_base(tn), top_node(0)
    {
    }

template <class T, class tree_node_allocator>
tree<T, tree_node_allocator>::fixed_depth_iterator::fixed_depth_iterator(const iterator_base& other)
    : iterator_base(other.node), top_node(0)
    {
    }

template <class T, class tree_node_allocator>
tree<T, tree_node_allocator>::fixed_depth_iterator::fixed_depth_iterator(const sibling_iterator& other)
    : iterator_base(other.node), top_node(0)
    {
    }

template <class T, class tree_node_allocator>
tree<T, tree_node_allocator>::fixed_depth_iterator::fixed_depth_iterator(const fixed_depth_iterator& other)
    : iterator_base(other.node), top_node(other.top_node)
    {
    }

template <class T, class tree_node_allocator>
bool tree<T, tree_node_allocator>::fixed_depth_iterator::operator==(const fixed_depth_iterator& other) const
    {
    if(other.node==this->node && other.top_node==top_node) return true;
    else return false;
    }

template <class T, class tree_node_allocator>
bool tree<T, tree_node_allocator>::fixed_depth_iterator::operator!=(const fixed_depth_iterator& other) const
    {
    if(other.node!=this->node || other.top_node!=top_node) return true;
    else return false;
    }

template <class T, class tree_node_allocator>
typename tree<T, tree_node_allocator>::fixed_depth_iterator& tree<T, tree_node_allocator>::fixed_depth_iterator::operator++()
    {
    assert(this->node!=0);

    if(this->node->next_sibling) {
        this->node=this->node->next_sibling;
        }
    else { 
        int relative_depth=0;
       upper:
        do {
            if(this->node==this->top_node) {
                this->node=0; // FIXME: return a proper fixed_depth end iterator once implemented
                return *this;
                }
            this->node=this->node->parent;
            if(this->node==0) return *this;
            --relative_depth;
            } while(this->node->next_sibling==0);
       lower:
        this->node=this->node->next_sibling;
        while(this->node->first_child==0) {
            if(this->node->next_sibling==0)
                goto upper;
            this->node=this->node->next_sibling;
            if(this->node==0) return *this;
            }
        while(relative_depth<0 && this->node->first_child!=0) {
            this->node=this->node->first_child;
            ++relative_depth;
            }
        if(relative_depth<0) {
            if(this->node->next_sibling==0) goto upper;
            else                          goto lower;
            }
        }
    return *this;
    }

template <class T, class tree_node_allocator>
typename tree<T, tree_node_allocator>::fixed_depth_iterator& tree<T, tree_node_allocator>::fixed_depth_iterator::operator--()
    {
    assert(this->node!=0);

    if(this->node->prev_sibling) {
        this->node=this->node->prev_sibling;
        }
    else { 
        int relative_depth=0;
       upper:
        do {
            if(this->node==this->top_node) {
                this->node=0;
                return *this;
                }
            this->node=this->node->parent;
            if(this->node==0) return *this;
            --relative_depth;
            } while(this->node->prev_sibling==0);
       lower:
        this->node=this->node->prev_sibling;
        while(this->node->last_child==0) {
            if(this->node->prev_sibling==0)
                goto upper;
            this->node=this->node->prev_sibling;
            if(this->node==0) return *this;
            }
        while(relative_depth<0 && this->node->last_child!=0) {
            this->node=this->node->last_child;
            ++relative_depth;
            }
        if(relative_depth<0) {
            if(this->node->prev_sibling==0) goto upper;
            else                            goto lower;
            }
        }
    return *this;

//
//
//  assert(this->node!=0);
//  if(this->node->prev_sibling!=0) {
//      this->node=this->node->prev_sibling;
//      assert(this->node!=0);
//      if(this->node->parent==0 && this->node->prev_sibling==0) // head element
//          this->node=0;
//      }
//  else {
//      tree_node *par=this->node->parent;
//      do {
//          par=par->prev_sibling;
//          if(par==0) { // FIXME: need to keep track of this!
//              this->node=0;
//              return *this;
//              }
//          } while(par->last_child==0);
//      this->node=par->last_child;
//      }
//  return *this;
    }

template <class T, class tree_node_allocator>
typename tree<T, tree_node_allocator>::fixed_depth_iterator tree<T, tree_node_allocator>::fixed_depth_iterator::operator++(int)
    {
    fixed_depth_iterator copy = *this;
    ++(*this);
    return copy;
    }

template <class T, class tree_node_allocator>
typename tree<T, tree_node_allocator>::fixed_depth_iterator tree<T, tree_node_allocator>::fixed_depth_iterator::operator--(int)
   {
    fixed_depth_iterator copy = *this;
    --(*this);
    return copy;
    }

template <class T, class tree_node_allocator>
typename tree<T, tree_node_allocator>::fixed_depth_iterator& tree<T, tree_node_allocator>::fixed_depth_iterator::operator-=(unsigned int num)
    {
    while(num>0) {
        --(*this);
        --(num);
        }
    return (*this);
    }

template <class T, class tree_node_allocator>
typename tree<T, tree_node_allocator>::fixed_depth_iterator& tree<T, tree_node_allocator>::fixed_depth_iterator::operator+=(unsigned int num)
    {
    while(num>0) {
        ++(*this);
        --(num);
        }
    return *this;
    }


// Sibling iterator

template <class T, class tree_node_allocator>
tree<T, tree_node_allocator>::sibling_iterator::sibling_iterator() 
    : iterator_base()
    {
    set_parent_();
    }

template <class T, class tree_node_allocator>
tree<T, tree_node_allocator>::sibling_iterator::sibling_iterator(tree_node *tn)
    : iterator_base(tn)
    {
    set_parent_();
    }

template <class T, class tree_node_allocator>
tree<T, tree_node_allocator>::sibling_iterator::sibling_iterator(const iterator_base& other)
    : iterator_base(other.node)
    {
    set_parent_();
    }

template <class T, class tree_node_allocator>
tree<T, tree_node_allocator>::sibling_iterator::sibling_iterator(const sibling_iterator& other)
    : iterator_base(other), parent_(other.parent_)
    {
    }

template <class T, class tree_node_allocator>
void tree<T, tree_node_allocator>::sibling_iterator::set_parent_()
    {
    parent_=0;
    if(this->node==0) return;
    if(this->node->parent!=0)
        parent_=this->node->parent;
    }

template <class T, class tree_node_allocator>
typename tree<T, tree_node_allocator>::sibling_iterator& tree<T, tree_node_allocator>::sibling_iterator::operator++()
    {
    if(this->node)
        this->node=this->node->next_sibling;
    return *this;
    }

template <class T, class tree_node_allocator>
typename tree<T, tree_node_allocator>::sibling_iterator& tree<T, tree_node_allocator>::sibling_iterator::operator--()
    {
    if(this->node) this->node=this->node->prev_sibling;
    else {
        assert(parent_);
        this->node=parent_->last_child;
        }
    return *this;
}

template <class T, class tree_node_allocator>
typename tree<T, tree_node_allocator>::sibling_iterator tree<T, tree_node_allocator>::sibling_iterator::operator++(int)
    {
    sibling_iterator copy = *this;
    ++(*this);
    return copy;
    }

template <class T, class tree_node_allocator>
typename tree<T, tree_node_allocator>::sibling_iterator tree<T, tree_node_allocator>::sibling_iterator::operator--(int)
    {
    sibling_iterator copy = *this;
    --(*this);
    return copy;
    }

template <class T, class tree_node_allocator>
typename tree<T, tree_node_allocator>::sibling_iterator& tree<T, tree_node_allocator>::sibling_iterator::operator+=(unsigned int num)
    {
    while(num>0) {
        ++(*this);
        --num;
        }
    return (*this);
    }

template <class T, class tree_node_allocator>
typename tree<T, tree_node_allocator>::sibling_iterator& tree<T, tree_node_allocator>::sibling_iterator::operator-=(unsigned int num)
    {
    while(num>0) {
        --(*this);
        --num;
        }
    return (*this);
    }

template <class T, class tree_node_allocator>
typename tree<T, tree_node_allocator>::tree_node *tree<T, tree_node_allocator>::sibling_iterator::range_first() const
    {
    tree_node *tmp=parent_->first_child;
    return tmp;
    }

template <class T, class tree_node_allocator>
typename tree<T, tree_node_allocator>::tree_node *tree<T, tree_node_allocator>::sibling_iterator::range_last() const
    {
    return parent_->last_child;
    }

// Leaf iterator

template <class T, class tree_node_allocator>
tree<T, tree_node_allocator>::leaf_iterator::leaf_iterator() 
   : iterator_base(0), top_node(0)
   {
   }

template <class T, class tree_node_allocator>
tree<T, tree_node_allocator>::leaf_iterator::leaf_iterator(tree_node *tn, tree_node *top)
   : iterator_base(tn), top_node(top)
   {
   }

template <class T, class tree_node_allocator>
tree<T, tree_node_allocator>::leaf_iterator::leaf_iterator(const iterator_base &other)
   : iterator_base(other.node), top_node(0)
   {
   }

template <class T, class tree_node_allocator>
tree<T, tree_node_allocator>::leaf_iterator::leaf_iterator(const sibling_iterator& other)
   : iterator_base(other.node), top_node(0)
   {
   if(this->node==0) {
      if(other.range_last()!=0)
         this->node=other.range_last();
      else 
         this->node=other.parent_;
      ++(*this);
      }
   }

template <class T, class tree_node_allocator>
typename tree<T, tree_node_allocator>::leaf_iterator& tree<T, tree_node_allocator>::leaf_iterator::operator++()
   {
    assert(this->node!=0);
    if(this->node->first_child!=0) { // current node is no longer leaf (children got added)
         while(this->node->first_child) 
              this->node=this->node->first_child;
         }
    else {
         while(this->node->next_sibling==0) { 
              if (this->node->parent==0) return *this;
              this->node=this->node->parent;
              if (top_node != 0 && this->node==top_node) return *this;
              }
         this->node=this->node->next_sibling;
         while(this->node->first_child)
              this->node=this->node->first_child;
         }
    return *this;
   }

template <class T, class tree_node_allocator>
typename tree<T, tree_node_allocator>::leaf_iterator& tree<T, tree_node_allocator>::leaf_iterator::operator--()
   {
    assert(this->node!=0);
    while (this->node->prev_sibling==0) {
        if (this->node->parent==0) return *this;
        this->node=this->node->parent;
        if (top_node !=0 && this->node==top_node) return *this; 
        }
    this->node=this->node->prev_sibling;
    while(this->node->last_child)
        this->node=this->node->last_child;
    return *this;
    }

template <class T, class tree_node_allocator>
typename tree<T, tree_node_allocator>::leaf_iterator tree<T, tree_node_allocator>::leaf_iterator::operator++(int)
   {
   leaf_iterator copy = *this;
   ++(*this);
   return copy;
   }

template <class T, class tree_node_allocator>
typename tree<T, tree_node_allocator>::leaf_iterator tree<T, tree_node_allocator>::leaf_iterator::operator--(int)
   {
   leaf_iterator copy = *this;
   --(*this);
   return copy;
   }


template <class T, class tree_node_allocator>
typename tree<T, tree_node_allocator>::leaf_iterator& tree<T, tree_node_allocator>::leaf_iterator::operator+=(unsigned int num)
   {
   while(num>0) {
      ++(*this);
      --num;
      }
   return (*this);
   }

template <class T, class tree_node_allocator>
typename tree<T, tree_node_allocator>::leaf_iterator& tree<T, tree_node_allocator>::leaf_iterator::operator-=(unsigned int num)
   {
   while(num>0) {
      --(*this);
      --num;
      }
   return (*this);
   }

#endif

// Local variables:
// default-tab-width: 3
// End: