From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <berenger@riken.jp>
X-Original-To: caml-list@sympa.inria.fr
Delivered-To: caml-list@sympa.inria.fr
Received: from mail2-relais-roc.national.inria.fr (mail2-relais-roc.national.inria.fr [192.134.164.83])
	by sympa.inria.fr (Postfix) with ESMTPS id 98B737EE6B
	for <caml-list@sympa.inria.fr>; Mon, 25 Nov 2013 02:36:16 +0100 (CET)
Received-SPF: None (mail2-smtp-roc.national.inria.fr: no sender
  authenticity information available from domain of
  berenger@riken.jp) identity=pra; client-ip=134.160.33.176;
  receiver=mail2-smtp-roc.national.inria.fr;
  envelope-from="berenger@riken.jp";
  x-sender="berenger@riken.jp"; x-conformance=sidf_compatible
Received-SPF: Pass (mail2-smtp-roc.national.inria.fr: domain of
  berenger@riken.jp designates 134.160.33.176 as permitted
  sender) identity=mailfrom; client-ip=134.160.33.176;
  receiver=mail2-smtp-roc.national.inria.fr;
  envelope-from="berenger@riken.jp";
  x-sender="berenger@riken.jp"; x-conformance=sidf_compatible;
  x-record-type="v=spf1"
Received-SPF: Pass (mail2-smtp-roc.national.inria.fr: domain of
  postmaster@postman.riken.jp designates 134.160.33.176 as
  permitted sender) identity=helo; client-ip=134.160.33.176;
  receiver=mail2-smtp-roc.national.inria.fr;
  envelope-from="berenger@riken.jp";
  x-sender="postmaster@postman.riken.jp";
  x-conformance=sidf_compatible; x-record-type="v=spf1"
X-IronPort-Anti-Spam-Filtered: true
X-IronPort-Anti-Spam-Result: AnsCAFSoklKGoCGwhWdsb2JhbABZvSyDA4EzDgEBAQoLCxsogiUBAQUnEUARCxgJFg8JAwIBAgFFEwgBAYd9vCkXjw4WhB0DiUCKcYNjhkSPBQ
X-IPAS-Result: AnsCAFSoklKGoCGwhWdsb2JhbABZvSyDA4EzDgEBAQoLCxsogiUBAQUnEUARCxgJFg8JAwIBAgFFEwgBAYd9vCkXjw4WhB0DiUCKcYNjhkSPBQ
X-IronPort-AV: E=Sophos;i="4.93,764,1378850400"; 
   d="scan'208";a="45096155"
Received: from postman4.riken.jp (HELO postman.riken.jp) ([134.160.33.176])
  by mail2-smtp-roc.national.inria.fr with ESMTP; 25 Nov 2013 02:36:14 +0100
Received: from postman.riken.jp (postman4.riken.jp [127.0.0.1])
	by postman.riken.jp (Postfix) with SMTP id BBE298280F1
	for <caml-list@inria.fr>; Mon, 25 Nov 2013 10:36:11 +0900 (JST)
Received: from [172.27.98.103] (rikad98.riken.jp [134.160.214.98])
	by postman.riken.jp (Postfix) with ESMTPA id A253F7F803F
	for <caml-list@inria.fr>; Mon, 25 Nov 2013 10:36:11 +0900 (JST)
Message-ID: <5292A98B.9010202@riken.jp>
Date: Mon, 25 Nov 2013 10:36:11 +0900
From: Francois Berenger <berenger@riken.jp>
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.0
MIME-Version: 1.0
To: caml-list@inria.fr
References: <1384873538.80445.YahooMailNeo@web160506.mail.bf1.yahoo.com>
In-Reply-To: <1384873538.80445.YahooMailNeo@web160506.mail.bf1.yahoo.com>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding: 7bit
X-PMX-Version: 6.0.0.2142326, Antispam-Engine: 2.7.2.2107409, Antispam-Data: 2013.11.25.12715
Subject: Re: [Caml-list] short-circuit in Real World Ocaml ch 3 deserves a
 comment

On 11/20/2013 12:05 AM, Jean Saint-Remy wrote:
> [...]
> The example code using pattern matching appears to be a "let rec"
> short-circuit which I believe deserves a comment in the book. It appears
> to be puzzling, we are binding a "zero" to the head of the list in order
> to drop it? I think it is a fine example of OCaml that should be
> encouraged, not just an isolated case.
>
> let rec drop_zero ls = match ls with
>    | [] -> []
>    | 0 :: tl -> drop_zero tl
>    | hd :: tl -> hd :: drop_zero tl
> ;;

Are we really speaking of some "real world" OCaml?

This code is not tail recursive and can be replaced
by a one liner using List.filter from the standard library.