Dan Ingalls has answered a similar report...
To resolve file in this:

!UndefinedObject methodsFor: 'ThingLab' stamp: 'di 10/20/1999 09:30'!
isPrototype
        "message defined here to prevent error of asking for the
prototype when the
        definition hasn't been filed in yet"

        ^ false! !

Bolot
-------

 Subject: Re: ThingLab installation problem
    Date: Wed, 20 Oct 1999 09:44:59 -0800
    From: Dan Ingalls <Dan.Ingalls at disney.com>
      To: "Jordan, Thomas" <Jordan at irs.fzk.de>
      CC: squeak at cs.uiuc.edu


>Dear Dan
>I tried to install ThingLab V2 on my Squeak 2.6 (windows-version), for
>developing a process simulation. When I try to file in "fileInAll.st" the
>"ThingLab_PreDefs" are filed in properly (?), but afterwards, when in-filing
>"ThingLab.cs" an error occurs:
>"Error: You may not create any more undefined objects-use nil".
>As I'm quite new to Squeak my efforts to trace back the error did not
>succeed in debugging.
>Is there any trivial fault? Could you help me?
>Thanks in advance
>Thomas J.

Thomas -

Thanks for the alert.  This occurs due to a change in Squeak's class
definition facility.  I found I was able to get it all to fileIn and
work in 2.6 by
including the following definition before filing in ThingLab.cs:

---------------------
!UndefinedObject methodsFor: 'ThingLab' stamp: 'di 10/20/1999 09:30'!
isPrototype
        "message defined here to prevent error of asking for the
prototype when the
        definition hasn't been filed in yet"

        ^ false! !
---------------------

I would set about doing a new release of these files, except I really
want to wait until we integrate this with Morphic.  ThingLab is just
crying to
have all its things (points, lines, midpointLines, etc) be morphs.  This
will take it out of the bounds of the browser, add color and let us
throw away
all the double-buffered display code that is already supported in
Morphic (student project waiting to happen ;-).  It would also be pretty
simple then
to integrate with 3D (is THIS ever a student project!!)

        - Dan






Hernan Wilkinson wrote:
> 
> Hi,
>     I just wanted to say that I tried to file in ThingLab in Squeak 2.6 and
> gave me an error when reading the file ThingLab.cs (after filing in
> ThingLab-Predefs.cs).
>     The error was:
>     "You may not create any more undefined object--use nil"
> 
>     It does not happen with 2.3
> 
>     Bye, Hernan.
> _____________________________________________
> Hern·n A. Wilkinson
> BitX S.A. Argentina
> Phone: (54-11) 4574-1544  Fax: (54-11)4573-3368
> Franco 3419 . 1er piso - (1419)- Buenos Aires - Argentina
> Web: www.bitx.com.ar