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=-0.9 required=5.0 tests=BAYES_00,FORGED_GMAIL_RCVD, FREEMAIL_FROM autolearn=no autolearn_force=no version=3.4.4 X-Google-Thread: 103376,64fe8f87aae99538 X-Google-Attributes: gid103376,domainid0,public,usenet X-Google-Language: ENGLISH,ASCII-7-bit Path: g2news1.google.com!postnews.google.com!a70g2000hsh.googlegroups.com!not-for-mail From: Maciej Sobczak Newsgroups: comp.lang.ada Subject: Re: How to return an empty aggregate Date: Fri, 4 Apr 2008 13:35:19 -0700 (PDT) Organization: http://groups.google.com Message-ID: References: <945217e8-ec37-4a33-9847-28e8e7d55798@59g2000hsb.googlegroups.com> <2c23eecd-d5bf-4320-b0cd-a45b584ddfe3@m36g2000hse.googlegroups.com> NNTP-Posting-Host: 85.3.220.129 Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit X-Trace: posting.google.com 1207341319 17421 127.0.0.1 (4 Apr 2008 20:35:19 GMT) X-Complaints-To: groups-abuse@google.com NNTP-Posting-Date: Fri, 4 Apr 2008 20:35:19 +0000 (UTC) Complaints-To: groups-abuse@google.com Injection-Info: a70g2000hsh.googlegroups.com; posting-host=85.3.220.129; posting-account=bMuEOQoAAACUUr_ghL3RBIi5neBZ5w_S User-Agent: G2/1.0 X-HTTP-UserAgent: Mozilla/5.0 (Macintosh; U; Intel Mac OS X; en-US; rv:1.8.1.13) Gecko/20080311 Firefox/2.0.0.13,gzip(gfe),gzip(gfe) Xref: g2news1.google.com comp.lang.ada:20821 Date: 2008-04-04T13:35:19-07:00 List-Id: On 4 Kwi, 17:38, george.p...@gmail.com wrote: > Good example is a factory. Should it have a > mechanism to register-unregister itself? Not necessarily. I might be as well selected at startup time by some other entity (in which case it is also a strategy). > In addition such > objects make sense in singleton form Yes and no. Yes, because it does not make any sense to destroy them and create again. No, because it is *not harmful* to destroy and create them again (see also the monostate pattern): F : Factory'Class := Make_Funny_Factory; Obj : Object := F.Make_Object; Above, factory F is a transient entity that is used just to create one object. It might be a singleton as well, but does not have to. > and likely involve some sort of > guarding mutexes or be implemented as protected or tasks. If it's stateless, then it does not need any protection - there is nothing to protect. > BTW in C++ > empty factory class will be fine due to implied constructor/ > destructor. The empty factory class will be fine in Ada as well. -- Maciej Sobczak * www.msobczak.com * www.inspirel.com