MODULE Mod1
 
IMPORT StdLog;
 
TYPE
	ancestor* = POINTER TO EXTENSIBLE RECORD
		i*: INTEGER
	END;
 
VAR
	ance: ancestor;
 
PROCEDURE (anc: ancestor) Start*, NEW, EXTENSIBLE;(**)
BEGIN
	StdLog.String ("Процедура предок")
END Start;
 
END Mod1.

MODULE Mod2
 
IMPORT StdLog, Mod1;
 
TYPE
	descendant = POINTER TO  RECORD (Mod1.ancestor)
		b: BYTE
	END;
 
VAR
	desce: descendant;
 
PROCEDURE (des: descendant) Start;(**)
VAR
	ance: Mod1.ancestor;
BEGIN
	NEW(ance);
	StdLog.String ("Процедура потомок");
	ance := desce
END Start;
 
BEGIN
	NEW(desce);
	desce.Start
END Mod2.

    PROCEDURE (des: descendant) Start;(**)
    VAR
    	ance: Mod1.ancestor;
    BEGIN
    	NEW(ance);
    	StdLog.String ("Процедура потомок");
    	des := ance(descendant)
    END Start;

 
PROCEDURE TypeTest (x: Mod1.ancestor);
  VAR y: Mod2.descendant;
BEGIN
  IF x IS Mod2.descendant THEN
    StdLog.String ("Приведение типа возможно"); StdLog.Ln;
    y := x(Mod2.descendant);
    y.i := 666;
    y.b := 42
  ELSE
    StdLog.String ("Приведение типа невозможно"); StdLog.Ln;
    x.i := 1337
  END
END TypeTest.
 
PROCEDURE Test*;
  VAR w: Mod2.descendant; q: Mod1.ancestor;
BEGIN
  NEW(w); TypeTest(w);
  NEW(q); TypeTest(q);
  q := w; TypeTest(q)
END Test;