

LocalSymbols(st)
[
  st:=NewStack();
  Verify(IsOnStack(st,"c"),False);
  PushStackFrame(st,fenced);
    AddToStack(st,"a");
    AddToStack(st,"b");
    Verify(IsOnStack(st,"a"),True);
    Verify(IsOnStack(st,"c"),False);
    Verify(FindOnStack(st,"a"),{});
    FindOnStack(st,"b")["set"]:=True;
    Verify(FindOnStack(st,"b"),{{"set",True}});
    PushStackFrame(st,unfenced);
      AddToStack(st,"c");
      Verify(IsOnStack(st,"c"),True);
      Verify(IsOnStack(st,"a"),True);
    PopStackFrame(st);

    PushStackFrame(st,fenced);
      AddToStack(st,"c");
      Verify(IsOnStack(st,"c"),True);
      Verify(IsOnStack(st,"a"),False);
    PopStackFrame(st);

  PopStackFrame(st);
  Verify(StackDepth(st),0);
];


