From owner-sc22wg5+sc22wg5-dom8=www.open-std.org@open-std.org Fri Dec 5 08:13:32 2014 Return-Path: X-Original-To: sc22wg5-dom8 Delivered-To: sc22wg5-dom8@www.open-std.org Received: by www.open-std.org (Postfix, from userid 521) id C462F35733E; Fri, 5 Dec 2014 08:13:31 +0100 (CET) Delivered-To: sc22wg5@open-std.org Received: from nag-j.co.jp (nag-j.co.jp [111.68.142.10]) by www.open-std.org (Postfix) with ESMTP id 6BB543571CA for ; Fri, 5 Dec 2014 08:13:25 +0100 (CET) Received: from Maru6 (218-42-159-105.cust.bit-drive.ne.jp [218.42.159.105]) (authenticated bits=0) by nag-j.co.jp (8.14.5/8.14.5) with ESMTP id sB57DPph093864 for ; Fri, 5 Dec 2014 16:13:28 +0900 (JST) (envelope-from malcolm@nag-j.co.jp) Message-ID: From: "Malcolm Cohen" To: "WG5" References: <20141204170247.9A28E35837D@www.open-std.org><20141205014042.EC050358538@www.open-std.org> <20141205063232.F38DA358705@www.open-std.org> In-Reply-To: <20141205063232.F38DA358705@www.open-std.org> Subject: Re: [ukfortran] (SC22WG5.5375) (j3.2006) Question on PURE subroutines Date: Fri, 5 Dec 2014 16:13:18 +0900 Organization: =?utf-8?B?5pel5pysTkFH?= MIME-Version: 1.0 Content-Type: text/plain; format=flowed; charset="utf-8"; reply-type=original Content-Transfer-Encoding: 8bit X-Priority: 3 X-MSMail-Priority: Normal Importance: Normal X-Mailer: Microsoft Windows Live Mail 15.4.3555.308 X-MimeOLE: Produced By Microsoft MimeOLE V15.4.3555.308 Sender: owner-sc22wg5@open-std.org Precedence: bulk Damian Rouson writes: <<< On a somewhat related note, Tom Clune suggested a while back that there be a “virtuous” attribute that would preclude any access to non-local state. From the standpoint of purely functional programming, I think this would remove a wart that exists with PURE procedures at least in terms of how many people would initially interpret the meaning of PURE. >>> Yes, I've seen this several times before (basically ever since PURE showed up). There are a lot of times that PURE as currently defined is sufficient for parallelism, but equally there are times when they are insufficient - even for pure functions. An attribute like WHITER_THAN_THE_DRIVEN_SNOW would not only improve performance in such cases, they would also give the user a stronger guarantee that he was not inadvertantly shooting himself in the foot. So far though I've not seen any reasonable spelling for such an attribute (FUNCTIONAL is the best I've noticed so far, and is pretty bad). And so far I've not seen much enthusiasm for Yet Another Attribute with arguably marginal benefits (in my estimation, PURE gets most of the benefits both from the point of view of performance and safety). Cheers, -- ................................Malcolm Cohen, Nihon NAG, Tokyo.