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Re: postscript newbie has questions

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On Wednesday, November 7, 2018 at 5:59:49 PM UTC-6, Eric Lovejoy wrote:
> One problem I am having a hard time with is understanding how to change a variable, after defining it. 

Tackling just this one question. Part of the difficulty I think you're
running into is that PostScript doesn't really have the same concept
of a *variable* that other programming languages have. Instead, it's
more useful to think in terms of *definitions*.

A definition is a binding of a name (usually) and another object in a 
dictionary. When you do

  /num 42 def

you have to use the slant character / to warn the interpreter not to 
just look up the name and fetch the value right then and there. And 
you'll have to use the same formula every time you *assign* a new
value to the "variable".

If the value is already on the stack, then you usually have to use
'exch' to get the pieces in the right order.

  % 42 already there
  /num exch def

Hopefully this much info is enough for you to solve your problem 
and move on. But don't hesitate with further questions or follow-ups.

Good luck with PostScript!

droog

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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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