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 OAA20428; Thu, 18 Apr 2002 14:09:37 +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 OAA20424 for ; Thu, 18 Apr 2002 14:09:36 +0200 (MET DST) Received: from leia.mandrakesoft.com (office.mandrakesoft.com [195.68.114.34]) by nez-perce.inria.fr (8.11.1/8.11.1) with ESMTP id g3IC9ZL03407 for ; Thu, 18 Apr 2002 14:09:35 +0200 (MET DST) Received: by leia.mandrakesoft.com (Postfix, from userid 505) id 719545B15; Thu, 18 Apr 2002 14:09:29 +0200 (CEST) To: John Max Skaller Cc: caml-list@inria.fr Subject: Re: [Caml-list] Is a Cow an Animal? References: <3CBE2CC8.1030407@ozemail.com.au> From: Pixel Date: 18 Apr 2002 14:09:29 +0200 In-Reply-To: Message-ID: User-Agent: Gnus/5.09 (Gnus v5.9.0) Emacs/21.2 MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: owner-caml-list@pauillac.inria.fr Precedence: bulk Pixel writes: [...] > http://merd.net/pixel/language-study/various/is-a-cow-an-animal/ocaml.listing > uses a variant for the kind (I just changed it, it was a string) > > I've still kept the class to allow sharing of fields. > > BUT this solution doesn't allow a stricter checking alike ocaml2.listing or > c++2.listing. The reason is that you can't parameter the class with values > (like (Vegetable Carrot)) only types. > > Maybe this is possible with polymorphic variants (?), I'll try... done: http://merd.net/pixel/language-study/various/is-a-cow-an-animal/ocaml3.listing it's quite nice. The advantage over the all-in-class solution is that it's easier to check the types: * one pb was: let is_meat_ = function | `Beef | `Dead_rabbit | `Dead_human -> true | _ -> false which type "[> `Beef | `Dead_rabbit | `Dead_human] -> bool" doesn't allow is_meat_ (food : [`Grass]) whereas let is_meat e = is_meat_ (e :> food_kind) is_meat (food : [`Grass]) is allowed (since is_meat : [< food_kind] -> bool) * I still can't manage to have: new_human : int -> ([ `Dead_human], [< food_kind]) animal all i got is new_human : int -> ([ `Dead_human], _[< food_kind]) animal Please help! ------------------- 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