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=1.2 required=5.0 tests=BAYES_00,FROM_WORDY, INVALID_MSGID autolearn=no autolearn_force=no version=3.4.4 X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: 103376,772ae8afc5db35f2 X-Google-Attributes: gid103376,public From: "Nick Roberts" Subject: Re: Single Extension; Polymorphic Arrays Date: 1999/03/09 Message-ID: <7c3oet$jr1$1@plug.news.pipex.net>#1/1 X-Deja-AN: 453057953 References: <36E40BD9.2652469B@averstar.com> X-MimeOLE: Produced By Microsoft MimeOLE V4.72.3110.3 Organization: UUNET WorldCom server (post doesn't reflect views of UUNET WorldCom) Newsgroups: comp.lang.ada Date: 1999-03-09T00:00:00+00:00 List-Id: Tucker Taft wrote in message <36E40BD9.2652469B@averstar.com>... [...] |Fundamentally, task and protected types and objects are special, because |they provide synchronization, and with synchronization, uniqueness makes |a big difference. [...] |-Tucker Taft stt@averstar.com http://www.averstar.com/~stt/ |Technical Director, Distributed IT Solutions (www.averstar.com/tools) |AverStar (formerly Intermetrics, Inc.) Burlington, MA USA And so, by extrapolation, I would argue that a single record extension declaration needs to be provided, because the (overriding) implementations of these objects may involve the need to enforce the singleness of interaction with other entities (including situations where synchronisation issues are important). It seems to me, therefore, that the necessity (or at least usefulness) of being able to prevent the creation of further copies of an object of an extended type is the same as for task and protected objects. (NB: I reiterate my understanding of how immensely difficult is the task of a designing a programming language.) ------------------------------------- Nick Roberts -------------------------------------