From mboxrd@z Thu Jan 1 00:00:00 1970 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me X-Spam-Level: X-Spam-Status: No, score=-1.9 required=5.0 tests=BAYES_00 autolearn=ham autolearn_force=no version=3.4.4 X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: 103376,744136b4fae1ff3e X-Google-Attributes: gid103376,public X-Google-ArrivalTime: 2003-03-13 01:45:50 PST Path: archiver1.google.com!news1.google.com!newsfeed.stanford.edu!news-spur1.maxwell.syr.edu!news.maxwell.syr.edu!newsfeed.icl.net!newsfeed.fjserv.net!newsfeed.icl.net!newsfeed.fjserv.net!feed.news.nacamar.de!fu-berlin.de!uni-berlin.de!213.155.153.242!not-for-mail From: Peter Amey Newsgroups: comp.lang.ada Subject: Re: [Spark] Converting Arrays Date: Thu, 13 Mar 2003 09:47:24 +0000 Organization: Praxis Critical Systems Message-ID: <3E7053AC.DB4C71DD@praxis-cs.co.uk> References: NNTP-Posting-Host: 213.155.153.242 Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Trace: fu-berlin.de 1047548748 68713058 213.155.153.242 (16 [69815]) X-Mailer: Mozilla 4.73 [en] (Windows NT 5.0; U) X-Accept-Language: en Xref: archiver1.google.com comp.lang.ada:35282 Date: 2003-03-13T09:47:24+00:00 List-Id: "Grein, Christoph" wrote: > > > The restriction that an out mode parameter can't be referenced in a > > precondition seems to be the major cause of the difficulty, and I have > > (reluctantly) come to the conclusion that the way to avoid explicit > > rules for each instance of the output parameter is to pass the length as > > an additional parameter, as Rod suggests. > > I've never used SPARK myself, but I've read the PDF excerpt of Barnes' book with > interest. > > I'm wondering whether it wouldn't be feasible to change the SPARK rules in such > a way to allow references of attributes of out parameters in preconditions. > (Even in Ada 83, where reading of out parameters was forbidden, reading of their > attributes and discriminants was allowed - and for a good reason.) That specific topic is the subject of an open "performance report" and we have been thinking about it for quite a while. FWIW, it is not something that has been identified as a significant problem for most SPARK users; however, that is no reason to ignore it for ever! Peter