Re: Problems with Victoria Day implementation of PCL

[kanderso@DINO.BBN.COM]

  Redistributed: CommonLoops.PA
  Date: Tue, 19 Jun 90 07:46:58 +0200
  From: Benoit HABERT <bh@litp.ibp.fr>
  To: CommonLoops.PA@xerox.com
  Subject: Problems with Victoria Day implementation of PCL
  
  
  I am using the PCL implementation
  Victoria Day to implement a parser (a chart parser, for
  unification based grammars).
  In the output files of the parser, I came accross items like:
        #<unknown-object 1306eab>
  Scanning Victoria-Day source files, I did not find the string
  "unknown-object"
  Furthermore, (make-instance 'unknown-object) triggers an error.
  There is no class named "unknown-object"
  
  While parsing the same text, with the same grammar and the same
  dictionary, I noticed that the "unknown-objects" appeared
  at slightly different places. For instance (I am using French
  Trade-Unions manifestos to test my parser):
  First parse of a text:
   e<quilibre  du  secteur  locatif  #<unknown-object 130547b>  entrai^\nant
  par
  ...
  As one can notice in these samples, these "unknown-objects" occur
  "in bursts", then do not appear for a while, and occur again.
  They replace seemingly punctuation marks which were represented
  as strings so as not to interfere with Common Lisp macro-
  characters. To test this hypothesis, I replaced in the test text
  strings like ";" by symbols like |;| and "unknown-objects" did
  not appear any more in the output files.
  Another hint: I did not came accross this problem with
  Rainy Day.
  
  
  Have you any idea about the origin of this problem, and any solution
  (apart from avoiding strings !)
  
  Benoit Habert
  
Off hand, this doesn't seem like a PCL problem.  Rather it seems like
a problem with your parser, or the LISP you are using, or perhaps some
interaction between them and PCL.  Are these unknown-objects PCL
instance?  What class are they?

k