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: 103376,3b98a26890a2d400 X-Google-Attributes: gid103376,public X-Google-ArrivalTime: 2003-01-17 08:35:10 PST Path: archiver1.google.com!news1.google.com!newsfeed.stanford.edu!logbridge.uoregon.edu!fu-berlin.de!uni-berlin.de!213.155.153.242!not-for-mail From: Peter Amey Newsgroups: comp.lang.ada Subject: Re: Keyword "null" Question Date: Fri, 17 Jan 2003 16:35:57 +0000 Organization: Praxis Critical Systems Message-ID: <3E2830ED.C37F586D@praxis-cs.co.uk> References: <3E281B97.76F47E30@noSpam.raytheon.com> 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 1042821307 23527722 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:33142 Date: 2003-01-17T16:35:57+00:00 List-Id: Michael Bustillo wrote: > > While reviewing the Ada LRM, it makes note that the Ada keyword "null" > does nothing except pass to the next statement. This seems intuitive > enough, however... > > I'm currently attempting to reverse engineer some code so that it can be > converted to another language, and I've run across the following: > > if SOME_EVENT_TOOK_PLACE then > null; > end if; > > This statement is simply standing alone by itself, not part of any > "case-like" structure or anything sneaky. I guess my question is when > it says "...it does nothing..." does it actually mean that it is putting > a NO OP there? Because then this would actually be doing something, > most likely a timing issue, and that's what I need to know. > > I appreciate your time, and thanks. I would have thought that this is most likely a hook for some planned future development. I have written code that cased or looped over an enumeration type with a single element for example where extension seemed likely. I am confident that the source statements would not generate any object code given any half-decent optimization. Peter