[Oberon] Eliminating RETURN statements

[Chris Burrows]

Not only that but the generated instructions are identical which proves that the two forms are equivalent.

However, the number of operators could be reduced by transforming it into a REPEAT statement. For example:

  PROCEDURE Fit(i, j: INTEGER): BOOLEAN;
    VAR k: INTEGER;
  BEGIN
    k := -1;
    REPEAT
      INC(k)
    UNTIL (k > piecemax[i]) OR (p[i, k] & puzzl[j + k]);
    RETURN k > piecemax[i]
  END Fit;

Personally I find that the absence of the NOTs make it easier to comprehend,

Regards,
Chris

> -----Original Message-----
> From: Jörg [mailto:joerg.straube at iaeth.ch]
> Sent: Thursday, 9 April 2020 6:55 PM
> To: ETH Oberon and related systems; Chris Burrows
> Subject: Re: [Oberon] Eliminating RETURN statements
> 
> Hans
> The generated code length of the two solutions is the same.
> J�rg
> 
> ?Am 09.04.20, 09:22 schrieb "Oberon im Auftrag von Hans Klaver" <oberon-
> bounces at lists.inf.ethz.ch im Auftrag von hklaver at dds.nl>:
> 
>     Chris Burrows wrote:
> 
>     >> 	PROCEDURE Fit (i, j: INTEGER): BOOLEAN;
>     >> 		VAR k: INTEGER;
>     >> 	BEGIN
>     >> 		k := 0;
>     >> 		WHILE (k <= piecemax[i]) & ~(p[i, k] & puzzl[j + k]) DO
>     >> 			INC(k)
>     >> 		END
>     >> 	RETURN k > piecemax[i]
>     >> 	END Fit;
>     >>
>     >>
>     >
>     > According to one of De Morgan's Laws
>     >
>     > i.e.   ~(A AND B) --> (~A OR ~B)
>     >
>     > the WHILE expression can be simplified to:
>     >
>     >    WHILE (k <= piecemax[i]) & (~p[i, k] OR ~puzzl[j + k]) DO
>     >
>     > However, I'm not convinced this is simpler. What do you think?
> 
>     I would say that simplification means 'bringing to a form with less
> operators', and here there are (slightly) more operators on the right side.
>     So I do not consider it a simplification.
> 
>     --
>     Hans Klaver
> 
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