itemlist.cpp

一个在linux下的shell的计算器

/*
 *
 *
 *
 */

#include <iostream>
#include <sstream>
#include "itemlist.h"
#include "exception.h"

using namespace std;

//
//
//
ItemList::ItemList(): Item()
{
 type = LIST;
 first = last = NULL;
}

//
//
//
ItemList::~ItemList()
{
 Clear();
}

//
//
//
void ItemList::Clear()
{
 Item *p = first, *q=NULL;
 while (p != NULL)
 {
  q = p->next;
  delete p;
  p = q;
 }
 first = last = NULL;
}

//
//
//
void ItemList::Add(Item *p)
{
 if (last == NULL) first = last = p;
 else 
 {
  last->next = p;
  p->prev = last;
  last = last->next; 
 }
}

//
//
//
Item *ItemList::First()
{
 return first;
}

//
//
//
Item *ItemList::Last()
{
 return last;
}


//
//
//
void ItemList::Remove(Item *p)
{
 Item *iprev = p->prev;
 Item *inext = p->next;
 if (iprev != NULL) iprev->next = inext;
 else first = inext;
 if (inext != NULL) inext->prev = iprev;
 else last = iprev;
 if (first != NULL) first->prev = NULL;
 if (last != NULL) last->next = NULL;
}

//
//
//
int ItemList::Length()
{
 Item *p;
 int c = 0;
 for (p=last;p!=NULL;p=p->prev) c++;
 return c;
}


//
//
//
Item *ItemList::Clone()
{
 Item *p;
 ItemList *l = new ItemList();
 for (p=first;p!=NULL;p=p->next) l->Add(p->Clone());
 return l;
}

//
//
//
string ItemList::ToString() const
{
 Item *p;
 ostringstream str;
 str << "{";
 for (p=first;p!=NULL;p=p->next)
   str << " " << p->ToString(); 
 str << " }";
 return str.str();
}