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: 103376,38fc011071df5a27 X-Google-Attributes: gid103376,public X-Google-ArrivalTime: 2003-06-16 09:57:42 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!diablo.theplanet.net!newspeer1-gui.server.ntli.net!ntli.net!news-hub.cableinet.net!blueyonder!internal-news-hub.cableinet.net!news-binary.blueyonder.co.uk.POSTED!53ab2750!not-for-mail User-Agent: Microsoft-Entourage/10.1.1.2418 Subject: Re: Ideas for Ada 200X From: Bill Findlay Newsgroups: comp.lang.ada Message-ID: References: <3EE7CC70.E1FD3A67@adaworks.com> <3EECA772.4B662024@adaworks.com> Mime-version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-transfer-encoding: 7bit Date: Mon, 16 Jun 2003 17:56:33 +0100 NNTP-Posting-Host: 80.195.75.181 X-Complaints-To: abuse@blueyonder.co.uk X-Trace: news-binary.blueyonder.co.uk 1055782662 80.195.75.181 (Mon, 16 Jun 2003 16:57:42 GMT) NNTP-Posting-Date: Mon, 16 Jun 2003 16:57:42 GMT Organization: blueyonder (post doesn't reflect views of blueyonder) Xref: archiver1.google.com comp.lang.ada:39258 Date: 2003-06-16T17:56:33+01:00 List-Id: On 16/6/03 17:19, in article bckqmc$ofm$1@a1-hrz.uni-duisburg.de, "Georg Bauhaus" wrote: > Bill Findlay wrote: > : > : shiftTally(shift)(dayOfWeek(month).tallyIndex).sortTally(s).nbRejects := > : idem + 1; > > Hm. How about renaming and access values? Unfortunately, there are significant restrictions on the types of objects that can be renamed; and explicitly using access values introduces aliasing, which is better avoided if possible. I posted the following to a thread with the same title a few weeks ago: On 3/6/03 14:36, "Bill Findlay" wrote: > As I see it there are several arguments in favour of the 'idem' proposal: > > 1. It lets the programmer indicate that the occurrences of the LHS in the RHS > are *necessarily* the same, and not contingently so, which makes the code more > self-documenting. > > 2. It removes a source of error in transcribing the LHS multiple times. > > 3. It allows more concisely readable code when the LHS is lengthy. > > 4. It provides functionality that it only partially available by means of much > clumsier renaming declarations, because not all objects can be renamed. > > 5. It requires the compiler to evaluate the lvalue of the LHS once and reuse > that lvalue as often as needed to evaluate the RHS. This has three potential > benefits: shorter code, faster execution, and once-only invocation of any side > effects. > > 6. It might make it somewhat easier for the compiler to generate > update-in-place object code, where the target architecture allows that and > where it offers a performance advantage. > > 7. It provides all the utility of C's multitude of combined assignment > operators with one small, compatible change to the syntax of operands. > (I specify C, rather than C++, to avoid getting into a argument about > overloading assignment). > > 8. It allows the expression of useful forms that C's combined assignment > operators cannot achieve (e.g. X := 1 - idem;). -- Bill-Findlay chez blue-yonder.co.uk ("-" => "")