Re: defining new character names?

[Lynn Winebarger]

On Wednesday 21 August 2002 23:12, Keith Wright wrote:
> I endorse everthing Ralf said about the need for multiple
> names for multiple purposes, without prejudice to the
> question of whether any of it is any good at all.
> 
> >       As for constants, there's no reason to believe we want
> > character names to be constant.  There's plenty of reason
> > to consider forms for setting constants, but this is not one of
> > them.
> 
> What is a settable constant if not a variable?

      By setting constants, I meant binding a name to a value
and that value not being allowed to change during its lifetime.
It's not quite the same as a "settable constant".

> How is this different from
>   (define separator #\tab)
>   (format #t "~a~a~a~%" a separator b)
>   (define separator #\space)
> ?
> 
> > Sure it's ugly, but some people like that sort of thing.
> 
> Surely they would like even better a beautiful thing of the same sort!
> 
     Beauty's in the eye of the beholder.  Maybe they like Perl.
     If you considered my last email's proposal of making character
names be variables evaluated in "character space", it might even
be useful for switching charactersets on the fly.  Slow, but it could
work.  Just swap in an entirely different table, and boom, the same
lambda will use different integers for the same character names. 
Of course, I don't know much about that problem, so that solution 
might not be useful at all.

> If there is another example of one that changes from fetching
> to defining based upon the number of arguments, then I suggest
> we kill it before it breeds.
> 
       Well, it's not particularly unusual as a way of getting/setting fields
of an object implemented by a letrec.  Although they'll only set, never
bind.

> > I just hope it's not a copyright violation, as it's almost
> > verbatim from the chez user's guide.
> 
> It is fair use to take a short quote for criticism.
> 
       My own attempt at facetiousness.  Dybvig's put the whole thing
on scheme.com, so you don't have to rely on my little outtake.  He 
puts it under the heading of I/O control operations.

Lynn