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!j1g2000prb.googlegroups.com!not-for-mail From: Maciej Sobczak Newsgroups: comp.lang.ada Subject: Re: How to return an empty aggregate Date: Sat, 5 Apr 2008 14:14:04 -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: 85.3.103.164 Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit X-Trace: posting.google.com 1207430044 8483 127.0.0.1 (5 Apr 2008 21:14:04 GMT) X-Complaints-To: groups-abuse@google.com NNTP-Posting-Date: Sat, 5 Apr 2008 21:14:04 +0000 (UTC) Complaints-To: groups-abuse@google.com Injection-Info: j1g2000prb.googlegroups.com; posting-host=85.3.103.164; 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:20842 Date: 2008-04-05T14:14:04-07:00 List-Id: On 5 Kwi, 18:04, george.p...@gmail.com wrote: > Can you provide non-academic example? For the empty record? I thought I did already. :-) This might be a challenge, because we have no judge that can say whether something is academic or not. Consider a logging system that is designed with OO in mind. There is a base interface with some operation(s) for logging and a bunch of concrete implementations for various log destinations - one for disk file, one for network output, one for database persistency, etc. The part of the program that does something useful takes Log'Class and feeds its log entries via given Log'Class parameter to whatever happens to be a concrete Log implementation - a classic strategy pattern. What would you do to... switch the logging off? I would create the derived (concrete) log that is *empty* and does nothing and pass it as Log'Class to wherever it is expected. It cannot be simpler than that. Is it academic? I would do it at the nearest opportunity. -- Maciej Sobczak * www.msobczak.com * www.inspirel.com