Path: news.daimi.aau.dk!news.uni-c.dk!sunic!sunic.sunet.se!newsfeed.tip.net!news.seinf.abb.se!nooft.abb.no!Norway.EU.net!EU.net!howland.reston.ans.net!xlink.net!nntp.gmd.de!nntp.darmstadt.gmd.de!news.th-darmstadt.de!isa.informatik.th-darmstadt.de!kuehne From: kuehne@sun46.isa.informatik.th-darmstadt.de (Thomas Kuehne) Newsgroups: comp.lang.beta Subject: unusual inner Date: 20 Jul 1995 12:37:56 GMT Organization: TU Darmstadt, Praktische Informatik Lines: 46 Distribution: world Message-ID: <3ulin4$h07@rs18.hrz.th-darmstadt.de> Reply-To: kuehne@isa.informatik.th-darmstadt.de NNTP-Posting-Host: sun46.isa.informatik.th-darmstadt.de I read the FAQ, an introductory script on BETA, and roughly follow the discussions on comp.lang.beta, but I never encountered an explanation to the unusual approach of refinement with 'inner'. Any other OO language I know (maybe SIMULA is an execption?) allows to reuse the code of the superclass, that is: Old code maybe freely inserted in new code. BETA does this upside-down: New code is inserted (at exactly one place) into old code. This is akin to higher-order functions in functional programming languages. Doesn't this approach hamper unexpected reuse? As far as I can judge the situation, a BETA program is not extendible (in the classical OO sense) unless the extension has been anticipated before. This calls for clairvoyance on behalf of the developer (which is backup-ed by the fact that patterns are non-virtual by default; a common reproach made to C++: A non virtual method can not be redefined in subclasses, which might be desirable in later development stages). I appreciate that allowing additions only, automatically produces subclasses, which are true subtypes. In fact, even behavioral subtyping seems to be ensured, this the superclass code is always executed. However, I wonder if the BETA scheme isn't a bit to strict in practice. I'd be grateful for experiences with this strict scheme and for rationals that led to this language design. Are there publications that elaborate on this particular choice? Best Regards, Thomas +---------------------------------------------------------------------------+ | Thomas Kuehne | | Institut fuer Systemarchitektur | | Fachgebiet praktische Informatik Tel.: 06151/165420 | | Technische Universitaet Darmstadt Fax.: 06151/165472 | | Magdalenenstr. 11c kuehne@isa.informatik.th-darmstadt.de | | D-64289 Darmstadt http://www.isa.informatik.th-darmstadt.de/~kuehne | | | +---------------------------------------------------------------------------+