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=-1.3 required=5.0 tests=BAYES_00,INVALID_MSGID autolearn=no autolearn_force=no version=3.4.4 X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: 103376,555956c1cdd22308 X-Google-Attributes: gid103376,public From: Matthew Heaney Subject: Re: Help - Constructors - ASAP. Date: 1998/07/31 Message-ID: #1/1 X-Deja-AN: 376530314 Sender: matt@mheaney.ni.net References: <6p75qi$rcj@news.latnet.lv> <6pi4jq$j73$1@nnrp1.dejanews.com> <6pqdr2$hn2$1@nnrp1.dejanews.com> NNTP-Posting-Date: Thu, 30 Jul 1998 18:34:44 PDT Newsgroups: comp.lang.ada Date: 1998-07-31T00:00:00+00:00 List-Id: tedennison@my-dejanews.com writes: > But what happens in the situation where the client (perhaps a different > developer) wants to make a child class with fields that *must* be > initialized? That seems a quite reasonable thing to do. But now the > class-wide "constructor" isn't valid anymore. It can still be called for this > new child object, but will return a garbage value. No. It will bomb (by raising CE) at the point of assignment, because of a tag mismatch. You'd be trying to assign an value of the parent type to an object of the child type, which is illegal, and you'll therefore get a tag mismatch at run-time. > The only way I can see around this problem is to *also* declare a primitive > constructor, and have the body of the class-wide consructor redispatch to > that. Never declare a constructor that is a primitive operation of the type.