Re: postscript newbie has questions

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NNTP-Posting-Date	Mon, 12 Nov 2018 08:12:11 -0600
From	Scott Hemphill <hemphill@hemphills.net>
Newsgroups	comp.lang.postscript
Subject	Re: postscript newbie has questions
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Date	Mon, 12 Nov 2018 09:12:11 -0500
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Eric Lovejoy <blicken@gmail.com> writes:

> Hello all, I am new to postscript programing, it is my first stack
> based programing language, my background is in C/C++, programing
> embedded systems.
>
>
>
> In any event, I have some basic operations I am trying to utilize, and
> things seem to not be working. keep in mind, I am very new to the
> postscript language. I am also working on a linux machine, using the
> ghostscript interpreter.
>
> One problem I am having a hard time with is understanding how to
> change a variable, after defining it.
>
> take this example:
>
> %arc takes x,y,radius,start degree, end degree.
> /r 144 def
> 0 0 r 0 360 arc
> 1 0 1 setrgbcolor
> stroke
>  4{ r -24 sub r
> 0 0 r 0 360 arc
> 0 1 0 setrgbcolor
> stroke} repeat
>
>
> my goal with this code snippet is to make incrementally smaller
> circles by decrimenting variable "r".
> This doesnt work,  I get one circle.
> I have tried a variety of /r -24 sub r, /r -24 sub /r, r -24 sub /r,
> etc. but nothing like this works. what Iam I doing wrong?

I assume you want to subtract 24 from the value of r.  If you subtract
-24 from the value of r, you will be adding 24 to its value.  So
something like this should work:

  /r r 24 sub def

Scott
-- 
Scott Hemphill	hemphill@alumni.caltech.edu
"This isn't flying.  This is falling, with style."  -- Buzz Lightyear

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postscript newbie has questions Eric Lovejoy <blicken@gmail.com> - 2018-11-07 15:59 -0800
  Re: postscript newbie has questions luser droog <luser.droog@gmail.com> - 2018-11-07 20:17 -0800
  Re: postscript newbie has questions Scott Hemphill <hemphill@hemphills.net> - 2018-11-12 09:12 -0500

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