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From: evan@SU-CSLI.ARPA (Evan Kirshenbaum)
Newsgroups: mod.computers.laser-printers
Subject: Re: Flaw in Postscript?
Message-ID: <8601150543.AA03691@ucbvax.berkeley.edu>
Date: Tue, 14-Jan-86 21:36:43 EST
Article-I.D.: ucbvax.8601150543.AA03691
Posted: Tue Jan 14 21:36:43 1986
Date-Received: Thu, 16-Jan-86 00:58:10 EST
References: <seiler@hudson.dec.com>
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Approved: laser-lovers@washington.arpa

>It would suffice in this case to allow ShowPage to be redefined by an N-up
>header that itself calls the previous definition of ShowPage (not the
>original version, which might be buggy or might not include desired
>accounting).  Is that possible in PostScript?  

This is exactly what is done.  You do something like:

mydict begin
  /OLDSHOWPAGE /showpage load def
  ...
end

/showpage {
  mydict begin
  ... OLDSHOWPAGE ...
  end } def

Thus the newly defined version of showpage calls the version most recently
defined (at the time of definition).  This allows bugfixes to rom code and
even allows such redefinitions to be nested.

Evan Kirshenbaum
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