// -*- Mode: C++ -*-

//         GiSTlist.h
//
// Copyright (c) 1996, Regents of the University of California
// $Header: /cvsroot/Tree-M/GiST/GiSTlist.h,v 1.1 2001/05/06 00:45:52 root Exp $

#ifndef GISTLIST_H
#define GISTLIST_H

// A template list package, which is handy.
template <class T>
struct GiSTlistnode {
	T entry;
	GiSTlistnode<T> *prev, *next;
};

template <class T>
class GiSTlist {
public:
	GiSTlist() { front=rear=NULL; }
//	GiSTlist(const GiSTlist<T>& l) { front=l.front; rear=l.rear; }
	int IsEmpty() { return front==NULL; }
	T RemoveFront() {
		assert(front!=NULL);
		GiSTlistnode<T> *temp=front;
		T e=front->entry;

		front=front->next;
		if(front) front->prev=NULL;
		else rear=NULL;
		delete temp;
		return e;
	}

	T RemoveRear() {
		assert(rear!=NULL);
		GiSTlistnode<T> *temp=rear;
		T e=rear->entry;

		rear=rear->prev;
		if(rear) rear->next=NULL;
		else front=NULL;
		delete temp;
		return e;
	}

	void Prepend(T entry) {
		GiSTlistnode<T> *temp=new GiSTlistnode<T>;

		temp->entry=entry;
		temp->next=front;
		temp->prev=NULL;
		if(rear==NULL) rear=temp;
		else front->prev=temp;
		front=temp;
	}

	void Append(T entry) {
		GiSTlistnode<T> *temp=new GiSTlistnode<T>;

		temp->entry=entry;
		temp->prev=rear;
		temp->next=NULL;
		if(front==NULL) front=temp;
		else rear->next=temp;
		rear=temp;
	}

//private:
	GiSTlistnode<T> *front, *rear;
};

#endif