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tester/testsuite/extensions/objects2/shapes.jl

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+class Node {
+  Shape elem;
+  Node next;
+
+  void setElem(Shape c) { elem = c; }
+
+  void setNext(Node n) { next = n; }
+
+  Shape getElem() { return elem; }
+
+  Node getNext() { return next; }
+}
+
+class Stack {
+  Node head;
+
+  void push(Shape c) {
+    Node newHead = new Node;
+    newHead.setElem(c);
+    newHead.setNext(head);
+    head = newHead;
+  }
+
+  boolean isEmpty() {
+    return head==(Node)null;
+  }
+
+  Shape top() {
+    return head.getElem();
+  }
+
+  void pop() {
+    head = head.getNext();
+  }
+}
+
+class Shape {
+  void tell () {
+    printString("I'm a shape");
+  }
+
+  void tellAgain() {
+     printString("I'm just a shape");
+  }
+}
+
+class Rectangle extends Shape {
+  void tellAgain() {
+    printString("I'm really a rectangle");
+  }
+}
+
+class Circle extends Shape {
+  void tellAgain() {
+    printString("I'm really a circle");
+  }
+}
+
+class Square extends Rectangle {
+  void tellAgain() {
+    printString("I'm really a square");
+  }
+}
+
+int main() {
+  Stack stk = new Stack;
+  Shape s = new Shape;
+  stk.push(s);
+  s = new Rectangle;
+  stk.push(s);
+  s = new Square;
+  stk.push(s);
+  s = new Circle;
+  stk.push(s);
+  while (!stk.isEmpty()) {
+    s = stk.top();
+    s.tell();
+    s.tellAgain();
+    stk.pop();
+  }
+  return 0;
+}