Re: Factory Pattern

[Georg Bauhaus <rm.tsoh+bauhaus@maps.futureapps.de>]

On Thu, 2007-07-26 at 06:02 -0700, Maciej Sobczak wrote:
> On 26 Lip, 13:01, Georg Bauhaus <rm.tsoh+bauh...@maps.futureapps.de>
> wrote:
> 
> > > > Why is being case-insensitive and allowing full Unicode
> > > > in identifiers schizophrenic?
> >
> > > Because the concept of "case" does not apply to all scripts.
> 
> Bingo, but not only. Some scripts do have the concept of "case", but
> the mapping between upper-case and lower-case is not 1:1. Or even
> better, the *length* of sequence changes with case. This introduces
> some funny effects when trying to decide whether two sequences have
> the same meaning.

What is funny about the effects of a transformation
function? I would expect a transformation
to result in something that is not identical, but reflecting
needs.  Just like a calendar date has a number
of literals because most of them must follow the local
conventions (e.g. in legal documents).
This precludes writing a canonical, technical, internal
representation in source documents.

Insofar as programming is a formal, human activity, I would
expect the mode of expression to be somewhere between formal
and prosaic.


>  In the case-insensitive programming language I would
> expect that changing the "case" of one character in the identifier
> will not change its semantics. How Ada guarantees this for Unicode?

Ada guarantees this by way of defining identifiers etc. in the RM.

> Or maybe is Ada case-insensitive only in the ASCII subset of Unicode?
> Sorry, I don't call it "well-designed".

That would indeed be strange.



> We can make something case-insensitive in order to *reduce* the number
> of characters that are effectively different; and we can provide
> support for Unicode in order to *increase* the number of different
> characters.

Being able to select characters reduces it again. (Computers
can help with checking the selection. They are already performing
more advanced checks. :-)  I think it is quite likely that
the large population using ideographic characters will
find it easier to use the words that they
know when the alternative is to learn English.
(I think the transcriptions using Latin characters have
never become popular in China.)

(Try having us communicate in Japanese. How long will the
training take? Slavic languages are already different for
those having grown up with one of the Latin-Saxon dialects.
Yet at least the grammars have similar structure. Not so
with Chinese.)

> In my very humble opinion both are bad ideas (even separately).

But why?

When I saw the Fortress language documents I thought, Oh God,
not that again! If my understanding is correct, "a" and "A"
in the same local scope are different identifiers, and "_a"
with a leading underscore adds bold face characteristics
to another a! And they happily reintroduce the white space
operator that is so aptly described by Bjarne Stroustrup.
(Robert Dewar (Spitbol) was credited by Ralph Griswold 
(SNOBOL4) for having replaced the white space operator with '?').

Perhaps the Fortress guys think it is cool to be able to write 
something like

   a A /= aA

Will the computer-denying academics learn that writing
programs is *not*, and should not be, the same as
writing a math paper? Lazy snobs!

Getting them out of their universities and laboratories and
have them change a handful of programs written by regular
programmers might help.

Enough steam for today, sorry!

 -- Georg