Re: [Caml-list] OCaml troll on Slashdot

[Oliver Bandel <oliver@first.in-berlin.de>]

On Wed, Mar 16, 2005 at 09:43:42AM -0800, brogoff wrote:
> On Wed, 16 Mar 2005, Jacques Garrigue wrote:
> > From: Yoann Padioleau <padiolea@irisa.fr>
> > > Jon Harrop <jon@ffconsultancy.com> writes:
> > > > In OCaml, non-tail-recursive functions are often faster than their tail
> > > > recursive equivalents for small inputs (e.g. short lists).
> > >
> > > really ? why ?
> >
> > Because tail-recursive versions do some extra work to ensure
> > tail-recursiveness. For instance building a list in reverse order, and
> > converting it back with List.rev at the end. This only pays off for
> > huge lists.
> 
> No doubt the implementors will want me guillotined for bringing this up again,
> but using the (still functional!) set_cdr! tail recursive functions, which do
> *not* reverse the list, are always faster than the non tail recursive
> list functions, even for small lists, at least in my experience.

And I experienced, that adding a "_rev" at the end of a function
often makes more sense than adding a List.rev inside.

Often some code produces a list and gives it to a function that
again creates a list, based on that data.
Then "_rev"^2 means _orig and all is going well.

If there are an odd number of "_rev"-functions,
a List.rev can be added *THEN* (instead of always feel
the necessity to provide "_orig"-functions instead of
"_rev"-functions.



Ciao,
   Oliver