C 迭代器

#include <iostream> #include <cstdlib>
using namespace  std;
template<class T,int ssize=100>
class MyList
{  T data[ssize];
int length;
public:
MyList (){length=0;}
void push_back(const T&i)
{
if(length>=ssize-1)exit(1);
data[length++]=i;
}
bool empty()
{
return(length==0);
}
class iterator;
friend class iterator;
class iterator
{
MyList&lst;
int index;
public:
iterator(MyList &l):lst(l)
{
index=0;
}
iterator(MyList &l,bool):lst(l)
{
index=l.length;
}
T operator*() const
{
if(index>=0)
return lst.data[index];
else
exit(1);
}
T operator++()
{
if(index>lst.length)
exit(2);
return lst.data[++index];
}
T operator++(int)
{
if(index>lst.length)
exit(3);
return lst.data[index++];
}
T operator--()
{
if(index<=0)
exit(4);
return lst.data[--index];
}
T operator--(int)
{
if(index<=0)
exit(5);
return lst.data[index--];
}
bool operator!=(const iterator &rv)const
{
return index!=rv.index;
}
bool operator==(const iterator &rv)const
{
return index==rv.index;
}
bool operator<=(const iterator &rv)const
{
return index<=rv.index;
}
bool operator<(const iterator &rv)const
{
return index<rv.index;
}
bool operator>=(const iterator &rv)const
{
return index>=rv.index;
}
bool operator>(const iterator &rv)const
{
return index>rv.index;
}
};
iterator begin()
{
return iterator(*this);
}
iterator end()
{
return iterator(*this,true);
}
};
int main()
{
MyList<int> lst;
lst.push_back(1);
lst.push_back(2);
lst.push_back(3);
lst.push_back(4);
MyList<int>::iterator iter=lst.begin();
cout<<"从表头到表尾：";
for (; iter!=lst.end();iter++)
cout<<*iter<<" ";
cout<<endl;
MyList<int>::iterator iterl=lst.end();
cout<<"从表尾到表头：";
iterl--;
for (; iterl>=lst.begin();iterl--)
cout<<*iterl<<" ";
cout<<*iterl<<endl;
}