}
54 return *this;
55 }
56 template
57 template
58 inline typename mtree::template leaf_iterator_impl
59 mtree::leaf_iterator_impl::operator - (size_t off)
60 {
61 leaf_iterator_impl iter(*this);
62 iter -= off;
63 return iter;
64 }
65 template
66 template
67 inline typename mtree::template leaf_iterator_impl&
68 mtree::leaf_iterator_impl::operator -= (size_t off)
69 {
70 while (off)
71 {
72 if (base_type::is_null()) break;
73 --(*this); --off;
74 }
75 return *this;
76 }
77 template
78 template
79 inline typename mtree::template leaf_iterator_impl
80 mtree::leaf_iterator_impl::begin() const
81 {
82 leaf_iterator_impl iter(*this);
83 iter.first(typename reverse_trait::type());
84 return iter;
85 }
86 template
87 template
88 inline typename mtree::template leaf_iterator_impl
89 mtree::leaf_iterator_impl::end() const
90 {
91 leaf_iterator_impl iter(*this);
92 if(tree_)
93 {
94 iter.off_ = tree_->size();
95 }
96 return iter;
97 }
（7）间隔层定位方法的实现，代码如下：
1 template
2 template
3 inline void mtree::leaf_iterator_impl::first(no_reverse_tag)
4 {
5 assert(tree_&&root_size());
6 forward_first();
7 }
8 template
9 template
10 inline void mtree::leaf_iterator_impl::first(reverse_tag)
11 {
12 assert(tree_&&root_size());
13 forward_last();
14 }
15 template
16 template
17 inline void mtree::leaf_iterator_impl::last(no_reverse_tag)
18 {
19 assert(tree_&&root_size());
20 forward_last();
21 }
22 template
23 template
24 inline void mtree::leaf_iterator_impl::last(reverse_tag)
25 {
26 assert(tree_&&root_size());
27 forward_first();
28 }
29 template
30 template
31 inline void mtree::leaf_iterator_impl::increment(no_reverse_tag)
32 {
33 assert(tree_);
34 off_!=tree_->size() forward_next() : first(no_reverse_tag());
35 }
36 template
37 template
38 inline void mtree::leaf_iterator_impl::increment(reverse_tag)
39 {
40 assert(tree_);
41 off_!=tree_->size() forward_prev() : first(reverse_tag());
42 }
43 template
44 template
45 inline void mtree::leaf_iterator_impl::decrement(no_reverse_tag)
46 {
47 assert(tree_);
48 off_!=tree_->size() forward_prev() : last(no_reverse_tag());
49 }
50 template
51 template
52 inline void mtree::leaf_iterator_impl::decrement(reverse_tag)
53 {
54 assert(tree_);
55 off_!=tree_->size() forward_next() : last(reverse_tag());
56 }
四、使用示例
（1）正向遍历某子树的所有叶子，代码如下：
1 mtree::iterator_base node;
2 mtree::leaf_iterator it = node;
3 mtree::leaf_iterator last = --it.end();
4 for (it = it.begin();it!=it.end();++it)
5 {
6 cout << *it;
7 if (it!=last)
8 cout <<" ";
9 }
（2）反向遍历某子树的所有叶子，代码如下：
1 mtree::iterator_base node;
2 mtree::reverse_leaf_iterator r_it = node;
3 mtree::reverse_leaf_iterator r_last = --r_it.end();
4 for (r_it = r_it.begin();r_it!=r_it.end();++r_it)
5 {
6 cout << *r_it;
7 if (r_it!=r_last)
8 cout <<" ";
9 }
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