[racket] question about foldl implementation

I just wanted to thank all of you for your insightful responses. This has
been very useful!
--Will K.

On Fri, Aug 13, 2010 at 3:21 PM, Will M. Farr <wmfarr at gmail.com> wrote:

> +1 from me, too.  I always have to check myself to remember that the foldl
> accumulator argument comes in on the *right*.  FWIW, OCaml also does it the
> Haskell way (foldl accumulator on the left, foldr accumulator on the right).
>
> This also makes the obvious many-argument version more efficient:
>
> (define (foldl kons knil . lists)
>  (if (ormap null? lists)
>    knil
>    (apply foldl kons (apply kons knil (map car lists)) (map cdr lists))))
>
> as opposed to
>
> (define (foldl* kons knil . lists)
>  (if (ormap null? lists)
>    knil
>    (apply foldl* kons (apply kons (append (map car lists) (list knil)))
> (map cdr lists))))
>
> The extra append is kinda annoying in the foldl* version....
>
> Will
>
> On Aug 13, 2010, at 4:18 PM, Matthias Felleisen wrote:
>
> >
> > I privately +1ed Joe, and I all supportive of introducing new folds and
> phasing out the old ones.
> >
> >
> > On Aug 13, 2010, at 4:04 PM, Sam Tobin-Hochstadt wrote:
> >
> >> On Fri, Aug 13, 2010 at 3:11 PM, Joe Marshall <jmarshall at alum.mit.edu>
> wrote:
> >>> It seems to me that the Haskell version is better.
> >>
> >> The Haskell ordering also has the advantage of fitting with the Typed
> >> Racket type system for variable-arity functions.
> >> --
> >> sam th
> >> samth at ccs.neu.edu
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