Linked lists (was Re: Typing system vs. Java

[Alex Martelli]

<xtian at hyperactive.co.nz> wrote in message
news:3b707aa4.591122937 at news.supernews.com...
    ...
> def cons(car, cdr):
>     return car, cdr
>
> x = cons(1, ())
> x -> (1, ())
> x = cons(2, x)
> x -> (2, (1, ()))
>
> (You'd have to do the proper cons(1, ()) to start it off - otherwise I
> guess it'd be a dotted pair.)

Uh, yes, cons does build a dotted-pair (and car and cdr access the
two halves of the pair) -- that's what they do in every LISP I know
(and () does look like a good representation for NIL) -- lists are
dotted-pairs of their head and their tail (with NIL being the cdr
at the end of the list).  Sorry for not pointing this out earlier!


> That's pretty spectacularly neat.
>
> Nice one, Alex.

Why, thanks -- it didn't look like anything special, and was meant
as more of a deadpan-humor quip (as in, "of COURSE you can build
LISP-ish linked lists, since you can build pairs and take them
apart again")...


Alex