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From: alo@kampi.hut.fi (Antti Louko)
Newsgroups: comp.lang.postscript
Subject: Re: The // operator
Message-ID: <22580@santra.UUCP>
Date: 6 Jun 89 07:56:01 GMT
References: <3903@imagen.UUCP>
Sender: news@santra.UUCP
Reply-To: alo@kampi.hut.fi (Antti Louko)
Organization: Helsinki University of Technology, Finland
Lines: 79

In article <3903@imagen.UUCP> geof@apolling (Geof Cooper) writes:
>Software developers, be careful how you use this feature.  It is not
>possible to test for the existence of a feature if you want to use // in
>relation to it.  For example, the latest Apple LaserPrep contains code
>of the form:
>
>	if <I'm a LaserWriter> then
>		<do some nifty things with funny operators in serverdict>
>
>This is all very well, but the "nifty thing" references LaserWriter
>operators in serverdict using the // convention.  This means that those
>names must resolve to valid objects on ALL machines, not just the
>LaserWriter, since the names are resolved in the scanner independent
>of the result of the conditional.
>
>- Geof

Software developers, you can use this little hack I just put together:
skipblock is a procedure which skips a %%BeginProcSet .. %%EndProcSet
region so that the interpreter won't scan the skipped text.

The only problem is how to get big companies to use this procedure...

    Antti

--------------------------------
%!

%%BeginProcSet: skipblock 1.0 0
/stoppedreadline {
  /savedhandler errordict /rangecheck get def
  errordict /rangecheck { pop stop } put
  { readline } stopped
  errordict /rangecheck /savedhandler load put
  { exch pop true dup }
  { false }
  ifelse
} bind def

/readlinehead {
  /-str- exch def
  /-file- exch def
  -file- -str- stoppedreadline
  {
    {
      -file- (..............) stoppedreadline not
      { pop pop exit} if
      pop pop
    } loop
  } if
} bind def

/skipblock {
  /-save- save def
  /str 600 string def
  /str2 600 string def
  currentfile str readlinehead not { stop } if
  (%%BeginProcSet:) anchorsearch
  { pop /-name- exch def } { stop } ifelse
  {
    currentfile str2 readlinehead not { stop } if
    (%%EndProcSet:) anchorsearch
    { pop -name- eq { exit } if } { pop } ifelse
  } loop
  -save- restore
} bind def
%%EndProcSet: skipblock 1.0 0

%example

skipblock
%%BeginProcSet: foobar
(This stuff should be skipped) ==
(This stuff should be skipped) ==
(This stuff should be skipped) ==
(This stuff should be skipped) ==
%%EndProcSet: foobar
(This stuff should not be skipped) ==
--------------------------------