Re: [BLACKBOX] Read-only IN parameters for all data types

From: [at]} <CFB>
Date: Thu, 21 Feb 2008 00:26:14 +1030

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> -----Original Message-----
> From: BlackBox [mailto:BLACKBOX{([at]})nowhere.xy
> Oleg N. Cher
> Sent: Wednesday, 20 February 2008 8:32 PM
> To: BLACKBOX{([at]})nowhere.xy
> Subject: Re: [BLACKBOX] Read-only IN parameters for all data types
>
> But, as shows experience, Delphi programmers more often
> do not like use the CONST in such a way.
> They prefer to use the most simple way of recording of
> transmitted parameters:
>
> PROCEDURE Do (a: INTEGER);
>

Are you sure that is the reason or is it just old Pascal habits? I often
simply forget to use CONST in my Delphi code because I spent so many years
coding in Pascal before it was introduced.

>
> Prof. Wirth is a good psychologist of programming.
> He knows that too big number of excessive possiblities
> generates bulky languages.

Yes, and he has also included CONST parameters in his latest (small)
language design Oberon-SA (2007).

>
> Instead of it I suggest to expand a way of use IN so:
>
> IF a IN {0..1000} THEN ... END;
>
> Current BlackBox realization does not accept such using of sets.
> But such way of recording is good and evident. What will say?
>

Sets are useful but large sets do suffer from hidden inefficiencies.
However, the example does not demonstrate their usefulness well as the
alternative is not too cumbersome:

  IF (a >= 0) & (a <= 1000) THEN ... END;

If you wanted to code something like this however,

 IF a IN {'a', 'e', 'i', 'o', 'u'} THEN

large sets might appear more attractive, but they are still not really
necessary as there is another alternative.

Oberon doesn't usually have several different ways of doing exactly the same
thing. In practice, these sorts of complex tests often are more suited to a
CASE statement than an IF statement. Consequently that is where you will
find a lot of flexibility with subranges and collections e.g.

    CASE s[i] OF
    'a', 'e', 'i', 'o', 'u':
      INC(vowels);
      INC(letters) |
    'A', 'E', 'I', 'O', 'U':
      INC(vowels);
      INC(letters);
      INC(capitals) |
    'b'..'d', 'f'..'h', 'j'..'n', 'p'..'t', 'v'..'z':
      INC(letters) |
    ...

Apologies for the biased choice of alphabet ;-)

Regards,
Chris

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Received on Wed Feb 20 2008 - 14:56:14 UTC