From: Benoit de Boursetty <debourse@email.enst.fr>
To: Pierre Weis <Pierre.Weis@inria.fr>
Cc: caml-list@inria.fr
Subject: Re: Ask for explanation -- possibly repeated
Date: Mon, 13 Dec 1999 01:25:14 +0100 (MET) [thread overview]
Message-ID: <Pine.GSO.4.02.9912130055340.26575-100000@young.enst.fr> (raw)
In-Reply-To: <199912122233.XAA12778@pauillac.inria.fr>
> ># let translate_tree =
> > let rec aux father (Classical_node (data, sons)) =
> > let rec this_node = Node (father, data,
> > List.map
> > (aux (Some this_node))
> > sons)
> > in this_node
> > in aux None
> > [ doesn't compile ]
> >So, is there an applicative workaround? I know how to do it with mutable
> >values / references, but...
>
> As usual: hide the side effect into the lazy side of the language that
> is usually considered as pure and applicative, add a bit of
> eta-expansion if your language does not know lazy evaluation properly,
> and you get a simple workaround:
>
> let translate_tree t =
> let rec aux father (Classical_node (data, sons)) =
> let rec this_node = lazy (Node (father, data,
> List.map
> (aux (Some (Lazy.force this_node)))
> sons))
> in Lazy.force this_node
> in aux None t;;
> val translate_tree : 'a classical_tree -> 'a tree = <fun>
Erm... "eta-expansion" is not that usual to me but... well, with all my
respect, your solution doesn't seem to work.
(unless it works with version 2.04, I'm still using O'CaML 2.02)
# let essai = Classical_node ("Father", [Classical_node ("Son", [])]);;
val essai : string classical_tree =
Classical_node ("Father", [Classical_node ("Son", [])])
# translate_tree essai;;
Stack overflow during evaluation (looping recursion?).
Ah ha. So are mutable values a must even outside the Lazy module? Or does
your eta-expansion (I don't even know what it means) need a lift... :-)
BdB.
next prev parent reply other threads:[~1999-12-13 16:27 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
1999-12-11 18:27 Damien Doligez
1999-12-12 22:33 ` Pierre Weis
1999-12-13 0:25 ` Benoit de Boursetty [this message]
1999-12-13 16:21 ` Pierre Weis
-- strict thread matches above, loose matches on Subject: below --
1999-12-08 5:07 Benoit de Boursetty
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