A Practical linked list

Even this linked list class has been used for a long time, and many unreasonable things have been ruled out. Some places do not want to use STL stuff. I feel that I can control and modify something I write, it can also run well, and if you have time, you can practice writing standard C ++ Code, especially if you want to practice templates, encapsulate abstractions, and so on. If you are lucky enough to be used by someone, you may feel very honored. If you find anything unreasonable, please leave a message for me.

/*************************************** ***************************
* File name: QDList. h
* File Description: two-way linked list
* Gysoft
**************************************** **************************/
Using namespace std;
# Define NULL 0

# Ifndef QDLIST_H
# Define QDLIST_H
Template <class T>
Class QDList;

/* --- Bidirectional linked list node class ---*/
Template <class T>
Class QDListNode
{
Friend QDList <T>;
Private:
T data;
QDListNode <T> * left, * right;
};

/* --- Two-way linked list ---*/

Template <class T>
Class QDList
{
Public:
QDList ();
~ QDList ();
Void RemoveAll ();
Void Append (const T & newData );
BOOL IsEmpty (ostream & out );
Bool RemoveAt (int nPos );
Int GetLength () const;
Int Search (const T & x, int & nPos );
Void Insert (int nPos, const T & x );
BOOL GetItem (int nPos, T & x );
// Void SortItem ();
Private:
QDListNode <T> * LeftEnd;
QDListNode <T> * RightEnd;
Int m_nLength;
};

/* --- Two-way linked list class: constructor ---*/
Template <class T>
QDList <T>: QDList ()
{
Leftend = rightend = NULL;
M_nlength = 0;
}

/* --- Two-way linked list class: destructor ---*/
Template <class T>
Qdlist <t> ::~ Qdlist ()
{
Removeall ();
}

/* --- Two-way linked list: Clear the linked list ---*/
Template <class T>
Void qdlist <t >:: removeall ()
{
Qdlistnode <t> * curr = leftend;
Qdlistnode <t> * next;

While (curr! = Rightend)
{
Next = curr-> right;
Delete curr;
Curr = next;
}

If (rightend) delete rightend;

Leftend = rightend = NULL;
M_nlength = 0;
};

/* --- Two-way linked list: Add a node at the end of the linked list ---*/
Template <class T>
Void qdlist <t >:: append (const T & newdata)
{
Qdlistnode <t> * newnode = new qdlistnode <t>;
Newnode-> DATA = newdata;
Newnode-> right = NULL;

If (leftend)
{
Newnode-> left = rightend;
Rightend-> right = newnode;
Rightend = newnode;
}
Else
{
Leftend = rightend = newnode;
Newnode-> left = newnode-> right = NULL;
Leftend = newnode;
}

M_nlength ++;
}

/* --- Two-way linked list: whether the output linked list is empty ---*/
Template <class T>
Bool qdlist <t >:: isempty (ostream & out)
{
If (! LeftEnd | m_nLength = 0)
{
Out <"Empty List! ";
Return TRUE;
}
Else
Return FALSE;

 
}

/* --- Two-way linked list: delete a linked list node ---*/
Template <class T>
Bool QDList <T>: RemoveAt (int nPos)
{
If (m_nLength = 0)
{
LeftEnd = RightEnd = NULL;
Return false;
}

QDListNode <T> * curr;
QDListNode <T> * next;

If (nPos <= 0)
{
Curr = LeftEnd;
Next = curr-> right;
Delete curr;
Leftend = next;
}
Else if (NPOs> = m_nlength)
{
Curr = rightend;
Next = curr-> left;
Delete curr;
Rightend = next;
}
Else
{
Curr = leftend;
While (NPOs)
{
Curr = curr-> right;
NPOs --;
}

Next = curr-> right;
Curr-> left-> right = next;
Next-> left = curr-> left;

Delete curr;
}
 
M_nlength --;
Return true;
};

/* --- Two-way linked list: Get the length of the linked list ---*/
Template <class T>
Int qdlist <t >:: getlength () const
{
Return m_nlength;
};

/* --- Two-way linked list: Find an element in the linked list ---*/
Template <class T>
Int qdlist <t>: Search (const T & X, Int & NPOs)
{
Qdlistnode <t> * curr = leftend;
NPOs =-1;
 
While (curr)
{
NPOs ++;
If (curr-> DATA = X)
{
Return NPOs;
}
Curr = curr-> right;
}
 
NPOs =-1;
Return NPOs;
};
/* --- Two-way linked list: Get the value of the specified position ---*/
Template <class T>
BOOL QDList <T>: GetItem (int nPos, T & x)
{
If (nPos <0 | nPos> m_nLength)
Return FALSE;
QDListNode <T> * curr = LeftEnd;
While (nPos> 1)
{
NPos --;
Curr = curr-> right;
}
X = curr-> data;
Return TRUE;

};
 

/* --- Two-way linked list: insert x --- */into nPos ---*/
Template <class T>
Void QDList <T>: Insert (int nPos, const T & x)
{
If (m_nLength = 0)
{
Append (x );
Return;
}

QDListNode <T> * newNode = new QDListNode <T>;
NewNode-> data = x;

If (nPos <= 0)
{
NewNode-> right = LeftEnd;
NewNode-> left = newNode;
LeftEnd = newNode;
}
Else if (nPos> = m_nLength)
{
NewNode-> left = RightEnd;
RightEnd-> right = newNode;
RightEnd = newNode;
}
Else
{
QDListNode <T> * curr = LeftEnd;

While (nPos> 1)
{
NPos --;
Curr = curr-> right;
}

QDListNode <T> * next = curr-> right;
NewNode-> left = curr;
Curr-> right = newNode;
NewNode-> right = next;
Next-> left = newNode;
}

M_nLength ++;
};

# Endif