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CTreeNode

CTreeNode is a class of the CTree binary tree node.

Description

CTreeNode provides the ability to work with nodes of the CTree binary tree. Options of navigation through the tree are implemented in the class. Besides, methods of working with the file are implemented.

Declaration

   class CTreeNode : public CObject

Title

   #include <Arrays\TreeNode.mqh>

Class Methods by Groups

Attributes

 

Owner

Gets/sets the pointer of the owner node

Left

Gets/sets the pointer of the left node

Right

Gets/sets the pointer of the right node

Balance

Gets the node balance

BalanceL

Gets the balance of the left sub-branch of the node

BalanceR

Gets the balance of the right sub-branch of the node

Creation of a new element

 

CreateSample

Creates a new node instance

Comparison

 

RefreshBalance

Recalculates the node balance

Search

 

GetNext

Gets the pointer of the next node

Input/Output

 

SaveNode

Saves the node data to a file

LoadNode

Downloads the node data from a file

virtual Type

Gets the identifier of the node type

Derived classes:

Trees of CTreeNode class descendants have practical application.

A descendant of CTreeNode class should have predefined methods: CreateSample creates a new instance of the descendant class of CTreeNode, Compare compares values of key fields of the descendant class of CTreeNode, Type (if it is necessary to identify a node), SaveNode and LoadNode (if it is necessary to work with a file).

Let's consider an example of a CTree descendant class.

//+------------------------------------------------------------------+
//|                                                   MyTreeNode.mq5 |
//|                        Copyright 2010, MetaQuotes Software Corp. |
//|                                       http://www.metaquotes.net/ |
//+------------------------------------------------------------------+
#property copyright "2010, MetaQuotes Software Corp."
#property link      "https://www.mql5.com"
//---
#include <Arrays\TreeNode.mqh>
//+------------------------------------------------------------------+
//| Describe CMyTreeNode class derived from CTreeNode.               |
//+------------------------------------------------------------------+
//| Class CMyTreeNode.                                               |
//| Purpose: Class of element of a binary tree.                      |
//|             Descendant of class CTreeNode.                       |
//+------------------------------------------------------------------+
class CMyTreeNode : public CTreeNode
  {
protected:
   //--- user's data
   long              m_long;            // key field of long type
   double            m_double;          // custom variable of double type
   string            m_string;          // custom variable of string type
   datetime          m_datetime;        // custom variable of datetime type
 
public:
                     CMyTreeNode();
   //--- methods of accessing user's data
   long              GetLong(void)                { return(m_long); }
   void              SetLong(long value)          { m_long=value;  }
   double            GetDouble(void)              { return(m_double); }
   void              SetDouble(double value)      { m_double=value;  }
   string            GetString(void)              { return(m_string); }
   void              SetString(string value)      { m_string=value;  }
   datetime          GetDateTime(void)            { return(m_datetime); }
   void              SetDateTime(datetime value)  { m_datetime=value;  }
   //--- methods for working with files
   virtual bool      Save(int file_handle);
   virtual bool      Load(int file_handle);
protected:
   virtual int       Compare(const CObject *node,int mode);
   //--- method of creating class instances
   virtual CTreeNode* CreateSample();
  };
//+------------------------------------------------------------------+
//| CMyTreeNode class constructor.                                   |
//| INPUT:  none.                                                    |
//| OUTPUT: none.                                                    |
//| REMARK: none.                                                    |
//+------------------------------------------------------------------+
void CMyTreeNode::CMyTreeNode()
  {
//--- initialization of user's data
   m_long        =0;
   m_double      =0.0;
   m_string      ="";
   m_datetime    =0;
  }
//+------------------------------------------------------------------+
//| Comparison with another tree node by the specified algorithm.    |
//| INPUT:  node - tree element to compare,                          |
//|         mode - identifier of comparison algorithm.               |
//| OUTPUT: result of comparison (>0,0,<0).                          |
//| REMARK: none.                                                    |
//+------------------------------------------------------------------+
int CMyTreeNode::Compare(const CObject *node,int mode)
  {
//--- mode parameter is ignored, because tree construction algorithm is the only one
   int res=0;
//--- explicit type casting
   CMyTreeNode *n=node;
   res=(int)(m_long-n.m_long);
//---
   return(res);
  }
//+------------------------------------------------------------------+
//| Creation of a new class instance.                                |
//| INPUT:  none.                                                    |
//| OUTPUT: pointer to a new instance of CMyTreeNode class.          |
//| REMARK: none.                                                    |
//+------------------------------------------------------------------+
CTreeNode* CMyTreeNode::CreateSample()
  {
   CMyTreeNode *result=new CMyTreeNode;
//---
   return(result);
  }
//+------------------------------------------------------------------+
//| Write tree node data to a file.                                  |
//| INPUT:  file_handle -handle of a file pre-opened for writing.    |
//| OUTPUT: true if OK, otherwise false.                             |
//| REMARK: none.                                                    |
//+------------------------------------------------------------------+
bool CMyTreeNode::Save(int file_handle)
  {
   uint i=0,len;
//--- checks
   if(file_handle<0) return(false);
//--- writing user data
//--- writing custom variable of long type
   if(FileWriteLong(file_handle,m_long)!=sizeof(long))          return(false);
//--- writing custom variable of double type
   if(FileWriteDouble(file_handle,m_double)!=sizeof(double))    return(false);
//--- writing custom variable of string type
   len=StringLen(m_string);
//--- write string length
   if(FileWriteInteger(file_handle,len,INT_VALUE)!=INT_VALUE)   return(false);
//--- write the string
   if(len!=0 && FileWriteString(file_handle,m_string,len)!=len) return(false);
//--- writing custom variable of datetime type
   if(FileWriteLong(file_handle,m_datetime)!=sizeof(long))      return(false);
//---
   return(true);
  }
//+------------------------------------------------------------------+
//| Read tree node data from a file.                                 |
//| INPUT:  file_handle -handle of a file pre-opened for reading.    |
//| OUTPUT: true if OK, otherwise false.                             |
//| REMARK: none.                                                    |
//+------------------------------------------------------------------+
bool CMyTreeNode::Load(int file_handle)
  {
   uint i=0,len;
//--- checks
   if(file_handle<0) return(false);
//--- reading
   if(FileIsEnding(file_handle)) return(false);
//--- reading custom variable of char type
//--- reading custom variable of long type
   m_long=FileReadLong(file_handle);
//--- reading custom variable of double type
   m_double=FileReadDouble(file_handle);
//--- reading custom variable of string type
//--- read the string length
   len=FileReadInteger(file_handle,INT_VALUE);
//--- read the string
   if(len!=0) m_string=FileReadString(file_handle,len);
   else       m_string="";
//--- reading custom variable of datetime type
   m_datetime=FileReadLong(file_handle);
//---
   return(true);
  }

 


Updated: 2016.03.23