Re: A Logical Model for Lists as Relations

From: David Cressey <dcressey_at_verizon.net>
Date: Thu, 11 May 2006 21:53:47 GMT
Message-ID: <LnO8g.6945$cR5.1617_at_trndny06>


"vc" <boston103_at_hotmail.com> wrote in message news:1147367048.051222.109730_at_u72g2000cwu.googlegroups.com...
> Jay Dee wrote:

> > See, I probably grok a successor operator, maybe a nil operator, but
> > I'm not tracking cons and am not sure why zero and nil differ.
>
> You do not know what the difference between the number zero and the
> empty list (Nil) is ?
>

Oh please, beware!!! If you look over the history of c.d.t. you'll some long, and excruciating diatribes on this very subject. It seems that, to some theoreticians, nothing is quite so interesting as nothing itself.

For information purposes, the operator "cons" is derived from Lisp, the first list processing language (AFAIK).
It constructs a list from an element and a list.

nil is a list with no list elements in it. For those of us who insisted on looking at lisp structures as if we were peering into the computer data structures themselves, nil might be described as a pointer that doesn't point at anything. But to a real lisp expert, this definition misses the point. (double meaning intended). Received on Thu May 11 2006 - 23:53:47 CEST

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