Re: [school-discuss] how to turn addpsx.pl into a subtraction worksheet generator

[Doug Loss <drloss@suscom.net>]

Jake Maul wrote:
> Greetings,
> First off, the script I'm referring to can be found here:
> http://www.seul.org/edu/packages/addpsx.pl
> It generates a 1-page postscript file containing random addition 
> problems. I was easily able to modify it to output multiplication problems:
>
>   $t=$a+$b;
>   ps_digits($a);
>   ps_digits("+ ".$b);
>   print "S\n";
>   # ps_digits($t);    # don't print answer
>   ps_digits("");      # skip a line instead
>
> Just change the "+ " to "x ". However, the same trick does not work with 
> subtraction: substituting in "- " causes errors. Ghostscript viewing 
> reports "undefined in d-", and an actual printout says "ERROR: 
> undefined. OFFENDING COMMAND: d-. STACK: -108".
>
> I've tried various things, such as backslashes before the -, and 
> separating the "- " out into a separate print line (which I thought 
> would work but generate funky output...didn't work, same error). Any ideas?
Jake,

   Send me the complete file as you've modified it and I'll put 
it on the SEUL/edu server as multpsx.pl.  I'm no PostScript 
hacker, but here's a guess: change the "+ " to " - " (a leading 
space).  Maybe that will break the concatenation of "d" and "-" 
that seems to be being misinterpreted.  The error you're seing 
isn't a Perl error, I'm pretty sure, but one coming from the 
PostScript interpreter in GhostScript.

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Doug Loss                 Courage is resistance to
Data Network Coordinator  fear, mastery of fear --
Bloomsburg University     not absence of fear.
dloss@bloomu.edu           Mark Twain