扮演“特性萃取机”角色,萃取各个迭代器的特性（迭代器的相应类型）
通过class template partial specialization的作用，不论是原生指针或class-type iterators,都可以让外界方便地取其相应类别
#pragma once
template <class T>
class MyIter
{
public:
MyIter(T *p = 0):ptr(p){}
MyIter(MyIter<T> &ths):ptr(ths.ptr){}
T& operator*(){return *ptr;}
typedef T value_type;
private:
T *ptr;
};
// Partial Specialization 偏特化
template <class T>
struct iterator_traitse
{
typedef typename T::value_type value_type;
};
template <class T>
struct iterator_traitse<T *>
{
typedef T value_type;
};
template <class T>
typename iterator_traitse<T *> :: value_type fun(T ite)
{
return *ite;
}
int main()
{
MyIter<int> ite(new int(8));
// cannot convert from ‘MyIter<T>‘ to ‘int‘
int n = fun(ite);
return 0;
}
原文：http://www.cnblogs.com/xiaobingqianrui/p/7764532.html