[Oberon] Eliminating RETURN statements

[Hans Klaver]

Chris Burrows wrote:

> 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,

Chris, I fully agree. Very elegant! The code can even be made slightly more elegant:

 (...)
   UNTIL (k > piecemax[i]) OR p[i, k] & puzzl[j + k]
   RETURN k > piecemax[i]
 END Fit;

One of the nice things of Oberon is that the precedence of the logical operators is emphasized by their size.
Because OR is larger than & , which is larger than ~ , it is easy to remember that

  a OR ~b & c  equals  (a) OR ((~b) & c)

The smaller the operator the more it 'binds' to the operand(s). The ~ operator binds most and so is evaluated first, the next in size, &, binds more than the larger OR and so & is evaluated before OR, which 'separates' its operands most and so is evaluated last. Easy! 

--
Hans Klaver