module virtualmenthods;
  //-------------------------------------------------------------
  class BasePacket;
    int A = 1;
    int B = 2;
    int C = 3;
  
    function void printA;
      $display("BasePacket::A is %d",A);
    endfunction : printA
  
    virtual function void printB;
      $display("BasePacket::B is %d",B);
    endfunction : printB
  
    virtual function void printC;
      $display("BasePacket::C is %d",C);
    endfunction : printC
  endclass : BasePacket
  //-------------------------------------------------------------
  class MyPacket1 extends BasePacket;
    int A = 4;
    int B = 5;
    int C = 6;
  
    function void printA;
      $display("MyPacket1::A  is %d",A);
    endfunction : printA
  
    function void printB;
      $display("MyPacket1::B  is %d",B);
    endfunction : printB
  
    virtual function void printC;
      $display("MyPacket1::C  is %d",C);
    endfunction : printC
  endclass : MyPacket1
  //-------------------------------------------------------------
  class ExtPacket extends MyPacket1;
    int A = 7;
    int B = 8;
    int C = 9;
  
    function void printA;
      $display("ExtPacket::A  is %d",A);
    endfunction : printA
  
    virtual function void printB;
      $display("ExtPacket::B  is %d",B);
    endfunction : printB

    // No printC function in ExtPacket
    // Inherit printC from MyPacket1
  endclass : ExtPacket
  //-------------------------------------------------------------
  
  BasePacket P1 = new;
  MyPacket1  P2 = new;
  ExtPacket  P3 = new;
  
  initial begin
    P1.printA; // displays ‘BasePacket::A is 1’
    P1.printB; // displays ‘BasePacket::B is 2’
    P1.printC; // displays ‘BasePacket::C is 3’
    //-----------------------------------------------------------
    P1 = P2; // P1 has a handle to a MyPacket1 object

    P1.printA; // displays ‘BasePacket::A is 1’
    P1.printB; // displays ‘MyPacket1::B  is 5’ - latest derived method
    P1.printC; // displays ‘MyPacket1::C  is 6’ - latest derived method

    P2.printA; // displays ‘MyPacket1::A  is 4’
    P2.printB; // displays ‘MyPacket1::B  is 5’
    P2.printC; // displays ‘MyPacket1::C  is 6’
    //-----------------------------------------------------------
    P1 = P3; // P1 has a handle to an ExtPacket object
    P2 = P3; // P2 has a handle to an ExtPacket object

    P1.printA; // displays ‘BasePacket::A is 1’
    P1.printB; // displays ‘ExtPacket::B  is 8’ - ???
    P1.printC; // displays ‘MyPacket1::C  is 9’ - ???
    
    P2.printA; // displays ‘MyPacket1::A  is 4’
    P2.printB; // displays ‘ExtPacket::B  is 8’ - ??? (virtual again???)
    P2.printC; // displays ‘MyPacket1::C  is 9’ - ??? (9???)
   
    P3.printA; // displays ‘ExtPacket::A  is 7’
    P3.printB; // displays ‘ExtPacket::B  is 8’
    P3.printC; // displays ‘MyPacket1::C  is 9’ - ??? (9???)
    //-----------------------------------------------------------
  end
endmodule