Path: news.daimi.aau.dk!poe
From: Jacob Seligmann <jas@systematic.dk>
Newsgroups: comp.lang.beta
Subject: Re: Constants in Beta
Date: 26 Apr 1995 08:48:41 GMT
Organization: DAIMI, Computer Science Dept. at Aarhus University
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Daniel Larsson <dlarsson@sw.seisy.abb.se> wrote:
> 
> Baiss E. Magnusson <BMagnusson@PrecisionImages.com> wrote:
> 
> > ...
> >
> > Now in a real world application these numbers would exist in a separate
> > <Defines> file and they would be reference by some constant name, or they
> > would be calculated based upon some environmental setting.
> >
> > This is accomplished in C with <#defines> so the above would be:
> > #define  H_WINDOW 100
> > ...
> >  do (H_WINDOW, V_WINDOW) -> position;
> >    (WINDOW_WIDTH, WINDOW_HEIGHT) -> size;
> > etc.
> >
> > What method in Beta would you use to replace all hard coded numeric
> > values with substitute <macro> values?
> 
> What is wrong with this?
> 
> H_WINDOW : (# exit 100 (* or whatever *) #)
> V_WINDOW : (# exit 100 (* or whatever *) #)
> 
> Patterns only exiting a constant is the Beta construct most closely
> corresponding to C #defines (only they are expressed within the
> language instead of a separate language)

Yes, and the 

      H_WINDOW: (# exit 100 #);
      V_WINDOW: (# exit 100 #);
   do 
      (H_WINDOW,V_WINDOW) -> position; 

approach is just as efficient as

   do (100,100) -> position

because the exit-values are inlined in the generated code.

/Jacob Seligmann
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