Re: [BLACKBOX] Order of calculating parameters

From: [at]} <Chris>
Date: Fri, 8 Feb 2013 07:02:08 +1030

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> -----Original Message-----
> From: BlackBox [mailto:BLACKBOX{([at]})nowhere.xy
> Sent: Friday, 8 February 2013 2:12 AM
> To: BLACKBOX{([at]})nowhere.xy
> Subject: [BLACKBOX] Order of calculating parameters
>
> Is the order of calculating parameters uniquely defined in standard of
> Component Pascal (or Oberon/Oberon-2)? I've this situation.
>
> PROCEDURE GetData (): INTEGER;
> BEGIN (* The data is taken from array "arr", indexed by var "idx". Order
> of taken data is one by one. *)
> INC(idx); RETURN arr[idx]
> END GetData;
>
> ...
> (* Example code: *)
> PutTile(GetData(), GetData(), GetData()); (* x, y, tile number *) ...
>

This is an good example of how *not* to use a procedure that has
side-effects.

See section 6.6.1 "Side-effects" in "Programming in Oberon" by Martin Reiser
and N Wirth:

"We emphasize that changes of global variables through side-effects of
functions is considered neither desirable practice nor good programming
style. Nevertheless, it is sometimes justified, as in the case of Uniform."
(Uniform is a rare good example which is given in the book).

Regards,

Chris Burrows
CFB Software
http://www.cfbsoftware.com

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Received on Thu Feb 07 2013 - 21:32:08 UTC