From mboxrd@z Thu Jan 1 00:00:00 1970 Received: (from majordomo@localhost) by pauillac.inria.fr (8.7.6/8.7.3) id UAA18208; Sat, 8 Jun 2002 20:30:44 +0200 (MET DST) X-Authentication-Warning: pauillac.inria.fr: majordomo set sender to owner-caml-list@pauillac.inria.fr using -f Received: from concorde.inria.fr (concorde.inria.fr [192.93.2.39]) by pauillac.inria.fr (8.7.6/8.7.3) with ESMTP id UAA18216 for ; Sat, 8 Jun 2002 20:30:42 +0200 (MET DST) Received: from nexus.stwing.upenn.edu (NEXUS.STWING.UPENN.EDU [165.123.132.61]) by concorde.inria.fr (8.11.1/8.11.1) with ESMTP id g58IUfH13349 for ; Sat, 8 Jun 2002 20:30:42 +0200 (MET DST) Received: from force.stwing.upenn.edu (daemon@force.stwing.upenn.edu [165.123.132.65]) by nexus.stwing.upenn.edu (8.11.6/8.11.6) with ESMTP id g58IUe015642 (using TLSv1/SSLv3 with cipher EDH-RSA-DES-CBC3-SHA (168 bits) verified NO); Sat, 8 Jun 2002 14:30:40 -0400 (EDT) Received: (from wlovas@localhost) by force.stwing.upenn.edu (8.11.6/8.11.6) id g58IUdv03934; Sat, 8 Jun 2002 14:30:39 -0400 (EDT) Date: Sat, 8 Jun 2002 14:30:39 -0400 From: William Lovas To: William Lee Irwin III Cc: Alessandro Baretta , Ocaml Subject: Re: [Caml-list] Compiler killer code? Message-ID: <20020608183039.GA3550@force.stwing.upenn.edu> Mail-Followup-To: William Lee Irwin III , Alessandro Baretta , Ocaml References: <3D02156D.7070303@baretta.com> <20020608143402.GQ6777@holomorphy.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20020608143402.GQ6777@holomorphy.com> User-Agent: Mutt/1.3.25i Sender: owner-caml-list@pauillac.inria.fr Precedence: bulk On Sat, Jun 08, 2002 at 07:34:02AM -0700, William Lee Irwin III wrote: > > Is the type inference algorithm guaranteed to termintate? I > > ask because I have accidentally attempted to evaluate a > > (meaningless) function which almost hanged my Athlon. > > The killer code is the following: > > type t = t -> t > > let f (x:t) :t = f f > > If I type this into the toplevel, it starts to allocate > > memory by the tens of megabytes, until I have to kill it to > > prevent a system crash. I let it reach approximately 128MB > > before killing it. (BTW, that was with ocaml 3.04+13 > > 2002-06-05.) > > Is the language really supposed to accept such garbage as > > that which I wrote? I wonder if it really would have crashed your system, or if O'Caml would have simply died with an `out of memory' error. > On Sat, Jun 08, 2002 at 04:32:13PM +0200, Alessandro Baretta wrote: > > I get this instead: > > # type t = t -> t;; > The type abbreviation t is cyclic If you use recursive types (`ocaml -rectypes'), it typechecks fine: # type t = t -> t;; type t = t -> t # let rec f (x : t) : t = f f;; val f : t = In fact, you don't even need to define the type abbreviation: # let rec f x = f f;; val f : 'a -> 'b as 'a = This is O'Caml 3.04 -- if it fails to typecheck in the CVS version, then i'd say either the semantics of recursive types have changed or a bug has been introduced. cheers, William ------------------- To unsubscribe, mail caml-list-request@inria.fr Archives: http://caml.inria.fr Bug reports: http://caml.inria.fr/bin/caml-bugs FAQ: http://caml.inria.fr/FAQ/ Beginner's list: http://groups.yahoo.com/group/ocaml_beginners