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 JAA16465; Thu, 11 Oct 2001 09:11:12 +0200 (MET DST)
X-Authentication-Warning: pauillac.inria.fr: majordomo set sender to owner-caml-list@pauillac.inria.fr using -f
Received: from nez-perce.inria.fr (nez-perce.inria.fr [192.93.2.78]) by pauillac.inria.fr (8.7.6/8.7.3) with ESMTP id JAA16742 for <caml-list@pauillac.inria.fr>; Thu, 11 Oct 2001 09:11:11 +0200 (MET DST)
Received: from bassia.wanadoo.fr (smtp-rt-5.wanadoo.fr [193.252.19.159])
	by nez-perce.inria.fr (8.11.1/8.10.0) with ESMTP id f9B7BAn19568
	for <caml-list@inria.fr>; Thu, 11 Oct 2001 09:11:10 +0200 (MET DST)
Received: from amyris.wanadoo.fr (193.252.19.150) by bassia.wanadoo.fr; 11 Oct 2001 09:11:09 +0200
Received: from debian (217.109.144.240) by amyris.wanadoo.fr; 11 Oct 2001 09:10:50 +0200
Received: from moi by debian with local (Exim 3.32 #1 (Debian))
	id 15ra05-0000Zq-00
	for <caml-list@inria.fr>; Thu, 11 Oct 2001 09:11:25 +0200
To: caml-list@inria.fr
Subject: Re: [Caml-list] Newbie question concerning type definitions
References: <3BC55BCA.15676.5F0873@localhost>
From: Remi VANICAT <vanicat@labri.u-bordeaux.fr>
Date: 11 Oct 2001 09:11:25 +0200
In-Reply-To: <3BC55BCA.15676.5F0873@localhost>
Message-ID: <87g08qejmq.dlv@wanadoo.fr>
User-Agent: Gnus/5.09 (Gnus v5.9.0) Emacs/21.0.105
MIME-Version: 1.0
Content-Type: text/plain; charset=iso-8859-1
Content-Transfer-Encoding: 8bit
Sender: owner-caml-list@pauillac.inria.fr
Precedence: bulk

"Thomas Link" <t.link.tmp200101@gmx.net> writes:

> Hello, 
> 
> I have hesitated to send this question to this mailing list as I 
> suspect it to be rather stupid. What am I trying to do? I would like to 
> implement a simple stack based language in OCaml in order to get a 
> feeling for OCaml and also to test some ideas. Well, I didn't get far 
> as I wasn't even able to define the basic data structures. I guess this 
> is plain wrong:
> 
> type returnState = Succeeded | Failed | Error of int
> and proc = (stack -> dictionary -> returnState) 
> and procs = proc list 
> and element = 
> 	Int of int 
>   | String of string
>   | Float of float
>   | Word of proc 
> and stack = element Stack.t 
> and dictionary = (string, procs) Hashtbl.t;; 
> 
> When compiling this, the compiler tells me that proc's definition is 
> cyclic. How can I circumvent this in OCaml? 

this is a FAQ (is this FAQ in the FAQ ?)
There is two possible answer :
First add the -rectype option to the compiler to allow such recursive
type, 

Secondly, put the proc type into a constructor :

type returnState = Succeeded | Failed | Error of int
and proc = Proc of (stack -> dictionary -> returnState) 
and procs = proc list 
and element = 
	Int of int 
  | String of string
  | Float of float
  | Word of proc 
and stack = element Stack.t 
and dictionary = (string, procs) Hashtbl.t;; 

-- 
Rémi Vanicat
vanicat@labri.u-bordeaux.fr
http://dept-info.labri.u-bordeaux.fr/~vanicat
-------------------
Bug reports: http://caml.inria.fr/bin/caml-bugs  FAQ: http://caml.inria.fr/FAQ/
To unsubscribe, mail caml-list-request@inria.fr  Archives: http://caml.inria.fr