今天爲了學習 c++標準程序庫 做鋪墊,學習了下c++ primer中的 模板與泛型編程
代碼粘帖如下:
#include<iostream>
#include<vector>
using namespace std;
template <class Type> class Queue;
template <class T>
std::ostream& operator<<(std::ostream&,const Queue<T>&);
template<class Type>class QueueItem
{
friend class Queue<Type>;
friend std::ostream& operator<< <Type>(std::ostream&,const Queue<Type>&);
QueueItem(const Type &t):item(t),next(0){};
Type item;
QueueItem *next;
};
template <class Type> class Queue
{
public:
Queue():head(0),tail(0){};
template<class It>
Queue(It beg,It end):head(0),tail(0)
{
copy_elems(beg,end);
}
Queue& operator=(const Queue& orig)
{
destroy();
copy_elems(orig);
return *this;
}
~Queue(){destroy();}
template <class Iter>void assign(Iter,Iter);
Type &front() {return head->item;}
const Type &front() const {return head->item;}
void push(const Type&);
void pop();
bool empty() const {return head==0;}
private:
friend std::ostream& operator<< <Type>(std::ostream&,const Queue<Type>&);
QueueItem<Type> *head;
QueueItem<Type> *tail;
void destroy();
void copy_elems(const Queue&);
template <class Iter> void copy_elems(Iter,Iter);
};
template <class Type> void Queue<Type>::push(const Type& val)
{
QueueItem<Type> *pt = new QueueItem<Type>(val);
if(empty())
head=tail=pt;
else
{
tail->next=pt;
tail=pt;
}
}
template <class Type> void Queue<Type>::pop()
{
QueueItem<Type> *pt=head;
head=head->next;
delete pt;
}
template <class Type> void Queue<Type>::destroy()
{
while(!empty())
pop();
}
template <class Type> void Queue<Type>::copy_elems(const Queue &orig)
{
for(QueueItem<Type> *pt=orig.head;pt;pt=pt->next)
push(pt->item);
}
template <class Type> template <class Iter >void Queue<Type>::copy_elems(Iter beg,Iter end)
{
while(beg!=end)
{
push(*beg);
++beg;
}
}
template <class Type> template<class Iter> void Queue<Type>::assign(Iter beg,Iter end)
{
destroy();
copy_elems(beg,end);
}
template <class Type> ostream& operator<<(ostream &os,const Queue<Type> &q)
{
os<<"<";
QueueItem<Type> *p;
for(p=q.head;p;p=p->next)
os<<p->item<<" ";
os<<">";
return os;
}
int main()
{
Queue<int> p1;
Queue<int> p2;
Queue<int> p3;
if(p1.empty())
Queue<int> p3;
if(p1.empty())
cout<<"p1 is empty"<<endl;
short s=1;
int i=2,m=3,n=4;
p1.push(s);
p1.push(i);
p1.push(m);
p1.push(n);
if(!p1.empty())
cout<<"p1 is not empty"<<endl;
cout<<"p1="<<p1<<endl;
p2=p1;
cout<<"p2="<<p2<<endl;
short a[4]={5,6,7,8};
Queue <int>p5(a,a+4);
cout<<"p5="<<p5<<endl;
vector<short> v(a,a+4);
p3.assign(v.begin(),v.end());
cout<<"p3="<<p3<<endl;
return 0;
}