迭代适配器(一) back_insert和front_insert的简单实现

//将vec的所有元素拷贝到以coll.begin()为起始地址的位置
copy(vec.begin(), vec.end(), coll.begin());

//将vec的所有元素拷贝到以coll.begin()为起始地址的位置
copy(vec.begin(), vec.end(), back_insert(coll.begin()));

 1 #ifndef ITERATOR_H
 2 #define ITERATOR_H
 3 #include <iterator>
 4 
 5 //BackInsertIterator
 6 template <typename Container>
 7 class BackInsertIterator
 8 {
 9 public:
10     typedef typename Container::value_type value_type;
11 
12     explicit BackInsertIterator(Container &cont)
13         :_cont(cont)
14     { }
15 
16     BackInsertIterator<Container> &operator= (const value_type &val)
17     {
18         _cont.insert(_cont.end(), val);
19         return *this;
20     }
21 
22     BackInsertIterator<Container> &operator*()
23     { return *this; }
24 
25     BackInsertIterator<Container> &operator++()
26     { return *this; }
27 
28     BackInsertIterator<Container> &operator++(int)
29     { return *this; }
30 private:
31     Container &_cont;
32 };
33 
34 template <typename Container>
35 BackInsertIterator<Container> backInsert(Container &c)
36 { return BackInsertIterator<Container>(c); }
37 
38 
39 //FrontInsertIterator
40 template <typename Container>
41 class FrontInsertIterator
42 {
43 public:
44     typedef typename Container::value_type value_type;
45 
46     explicit FrontInsertIterator(Container &cont)
47         :_cont(cont)
48     { }
49 
50     FrontInsertIterator<Container> &operator= (const value_type &val)
51     {
52         _cont.insert(_cont.begin(), val);
53         return *this;
54     }
55 
56     FrontInsertIterator<Container> &operator*()
57     { return *this; }
58 
59     FrontInsertIterator<Container> &operator++()
60     { return *this; }
61 
62     FrontInsertIterator<Container> &operator++(int)
63     { return *this; }
64 private:
65     Container &_cont;
66 };
67 
68 template <typename Container>
69 FrontInsertIterator<Container> frontInsert(Container &c)
70 { return FrontInsertIterator<Container>(c); }
71 
72 #endif