Hi Roger;

Okay... you mean it fails if []io is undefined. I'd say that 'depends on the
existence of X' and 'depends on the value of X' are distinct enough not to
be coverable by 'depends on X' I'm also young enough to barely remember IO
IMPLICIT ERROR's. I also got used to using the zilde (0 overstrike ~) which
probably was what generated the idea of a: in the first place, but I wasn't
on that plane ride.

------------------------------------------------------------------------
|\/| Randy A MacDonald   | APL: If you can say it, it's done.. (ram)
|/\| [EMAIL PROTECTED]  |
|\ |                     | The only real problem with APL is that
BSc(Math) UNBF'83        | it is "still ahead of its time."
Sapere Aude              |     - Morten Kromberg
Natural Born APL'er      | Demo website: http://156.34.68.75/
-----------------------------------------------------(INTP)----{ gnat }-

----- Original Message ----- 
From: "Roger Hui" <[EMAIL PROTECTED]>
To: "General forum" <[email protected]>
Sent: Friday, March 16, 2007 4:31 PM
Subject: Re: [Jgeneral] definition of a:


> Execute foo in your APL where
>
> {del} z {is} foo ; {quadio}
>       z {is} {iota} 0
> {del}
>
>
>
> ----- Original Message -----
> From: ramacd <[EMAIL PROTECTED]>
> Date: Friday, March 16, 2007 12:19 pm
> Subject: Re: [Jgeneral] definition of a:
>
> > Hi Roger;
> >
> > Ok, I'm stumped: how does {iota}0 depend on {quad}io?
> >
> > >: ...
>
>
>
> > ----- Original Message ----- 
> > From: "Roger Hui" <[EMAIL PROTECTED]>
> > To: "General forum" <[email protected]>
> > Sent: Friday, March 16, 2007 12:49 PM
> > Subject: Re: [Jgeneral] definition of a:
> >
> >
> > > I started using  {rho}0  to denote the empty list
> > > in APL because (a) it is shorter than 0{rho}0
> > > (b) it does not depend on {quad}io like {iota}0
> > > does (c) it has right "type" where '' does not.
> > > >From APL to J  {rho}0  got changed to $0.
> > >
> > > Of course strictly speaking it should be "an empty
> > > list" rather than "the empty list".  But the
> > > differences between the various empty lists are
> > > more amusing than significant.  When I was a mere
> > > pup I used to pester and annoy the APL implementers
> > > with questions like:  What is the difference
> > > between  ({iota}0),''   and   '',({iota}0)  and why?
> > > I guess payback exists after all.
> > >
> > >
> > >
> > > ----- Original Message -----
> > > From: [EMAIL PROTECTED]
> > > Date: Wednesday, March 14, 2007 1:56 pm
> > > Subject: Re: [Jgeneral] definition of a:
> > >
> > > > The" weather" comment is funny but as I said: "I am from a
> > > > different
> > > > cultural background" so making fun of my mistakes in English
> > is
> > > > fine with
> > > > me,since I have a good sense of humor.
> > > >
> > > > The empty list is exactly what I wanted (refer to the early
> > > > discussions of
> > > > <i.0
> > > >
> > > > The question was, as everyone can read from my earlier post:
> > > > Roger ! any enlightening  comment ?
> ----------------------------------------------------------------------
> For information about J forums see http://www.jsoftware.com/forums.htm

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