From: skaller <skaller@users.sourceforge.net>
To: Jeffrey Loren Shaw <shawjef3@msu.edu>
Cc: caml-list@inria.fr
Subject: Re: [Caml-list] lazy evaluation of combinator parsers
Date: Sat, 24 Mar 2007 17:48:03 +1100 [thread overview]
Message-ID: <1174718883.7517.46.camel@rosella.wigram> (raw)
In-Reply-To: <E1HUv3J-0002P1-Bt@sys29.mail.msu.edu>
On Fri, 2007-03-23 at 21:28 -0400, Jeffrey Loren Shaw wrote:
> let alt p1 p2 xs = append (p1 xs) (p2 xs)
>
> (* regex ? *)
> let opt a = alt a epsilon
>
> let rec recseq a =
> seq
> a
> (recseq a)
>
> (* regex * *)
> let rec star a =
> recseq (opt a)
>
> However, "star (symbol 'a')" causes a stack overflow. I'm not sure why,
> since my seq and alt functions are lazy.
Arguments are evaluated right to left eagerly, so
let rec recseq a = seq a (recseq a)
is instantly an infinite loop. seq is not called here,
it's second argument diverges.
--
John Skaller <skaller at users dot sf dot net>
Felix, successor to C++: http://felix.sf.net
prev parent reply other threads:[~2007-03-24 6:48 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-03-24 1:28 Jeffrey Loren Shaw
2007-03-24 6:48 ` skaller [this message]
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