te
38 inline void mtree::pre_iterator_impl::increment(reverse_tag)
39 {
40 assert(tree_&&off_<=tree_->size());
41 off_!=tree_->size() forward_prev() : first(reverse_tag());
42 }
43 template
44 template
45 inline void mtree::pre_iterator_impl::decrement(no_reverse_tag)
46 {
47 assert(tree_&&off_<=tree_->size());
48 off_!=tree_->size() forward_prev() : last(no_reverse_tag());
49 }
50 template
51 template
52 inline void mtree::pre_iterator_impl::decrement(reverse_tag)
53 {
54 assert(tree_&&off_<=tree_->size());
55 off_!=tree_->size() forward_next() : last(reverse_tag());
56 }
四、使用示例
（1）正向遍历整颗树，代码如下：
1 mtree mt;
2 mtree::iterator_base root = mt.get_root();
3 mtree::pre_iterator it = root;
4 mtree::pre_iterator last = --it.end();
5 for (it = it.begin();it!=it.end();++it)
6 {
7 cout << *it;
8 if (it!=last)
9 cout <<" ";
10 }
（2）反向遍历整颗树 ，代码如下：
1 mtree mt;
2 mtree::iterator_base root = mt.get_root();
3 mtree::reverse_pre_iterator r_it = root;
4 mtree::reverse_pre_iterator r_last = --r_it.end();
5 for (r_it = r_it.begin();r_it!=r_it.end();++r_it)
6 {
7 cout << *r_it;
8 if (r_it!=r_last)
9 cout <<" ";
10 }
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