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: 103376,1b417df64012e6d3 X-Google-Attributes: gid103376,public X-Google-ArrivalTime: 2002-03-17 13:53:04 PST Path: archiver1.google.com!news1.google.com!newsfeed.stanford.edu!news-spur1.maxwell.syr.edu!news.maxwell.syr.edu!newspeer.monmouth.com!newscon02.news.prodigy.com!newsmst01.news.prodigy.com!prodigy.com!postmaster.news.prodigy.com!newssvr11.news.prodigy.com.POSTED!not-for-mail From: "Pat Rogers" Newsgroups: comp.lang.ada References: <%12l8.9656$%_6.1717935@news11-gui.server.ntli.net> <3C94F235.80C7166A@adaworks.com> Subject: Re: tasks, protected types and entries X-Priority: 3 X-MSMail-Priority: Normal X-Newsreader: Microsoft Outlook Express 6.00.2600.0000 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2600.0000 Message-ID: <1f8l8.12464$yb3.3172535409@newssvr11.news.prodigy.com> NNTP-Posting-Host: 208.191.177.131 X-Complaints-To: abuse@prodigy.net X-Trace: newssvr11.news.prodigy.com 1016401981 ST000 208.191.177.131 (Sun, 17 Mar 2002 16:53:01 EST) NNTP-Posting-Date: Sun, 17 Mar 2002 16:53:01 EST Organization: Prodigy Internet http://www.prodigy.com X-UserInfo1: OP]QRACE[BWMQ_H]]ZN@_TDAYZOZ@GXOXR]ZMVMHQAVTUZ]CLNTCPFK[WDXDHV[K^FCGJCJLPF_D_NCC@FUG^Q\DINVAXSLIFXYJSSCCALP@PB@\OS@BITWAH\CQZKJMMD^SJA^NXA\GVLSRBD^M_NW_F[YLVTWIGAXAQBOATKBBQRXECDFDMQ\DZFUE@\JM Date: Sun, 17 Mar 2002 21:53:01 GMT Xref: archiver1.google.com comp.lang.ada:21380 Date: 2002-03-17T21:53:01+00:00 List-Id: "Richard Riehle" wrote in message news:3C94F235.80C7166A@adaworks.com... > "chris.danx" wrote: > > > What is the difference between an entry and a procedure? > > This is one of the most important and least often address issue > in Ada. In my classroom, after we have started our unit on > tasking, I have my students recite, in unison, > > "An entry has a queue." Unless the Real-Time Annex is used, with the Ceiling_Locking policy. Then there is no need for a queue. > > That is so fundamental, and so overlooked. I believe it is a > starting point for understanding all the associated mechanisms. > The properties of the queue itself, and behavior of its enclosing > task or protected object can be understood only when one > grasps this simple idea. Yet I encounter programmers who > have been using Ada for years who still don't know this. > > > ... a procedure will always execute regardless of any > > condition, but that an entry can have a guard to allow/prevent its execution > > if a given condition is satisfied. > > There are no guards on subprograms (procedures and functions). If there > were, they would be called pre-conditions. In fact, protected entry > barriers, and task entry guards, are simply a variation-on-the-theme of > pre-conditions. > > Richard Riehle >