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=0.2 required=5.0 tests=BAYES_00,INVALID_MSGID, REPLYTO_WITHOUT_TO_CC autolearn=no autolearn_force=no version=3.4.4 X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: 109fba,b87849933931bc93 X-Google-Attributes: gid109fba,public X-Google-Thread: fac41,b87849933931bc93 X-Google-Attributes: gidfac41,public X-Google-Thread: 1108a1,b87849933931bc93 X-Google-Attributes: gid1108a1,public X-Google-Thread: 114809,b87849933931bc93 X-Google-Attributes: gid114809,public X-Google-Thread: f43e6,b87849933931bc93 X-Google-Attributes: gidf43e6,public X-Google-Thread: 103376,b87849933931bc93 X-Google-Attributes: gid103376,public From: "Norman H. Cohen" Subject: Re: OO, C++, and something much better! Date: 1997/01/23 Message-ID: <32E774C4.534B@watson.ibm.com>#1/1 X-Deja-AN: 211696733 references: content-type: text/plain; charset=us-ascii organization: IBM Thomas J. Watson Research Center mime-version: 1.0 reply-to: ncohen@watson.ibm.com newsgroups: comp.lang.c++,comp.lang.smalltalk,comp.lang.eiffel,comp.lang.ada,comp.object,comp.software-eng x-mailer: Mozilla 3.0 (Win95; I) Date: 1997-01-23T00:00:00+00:00 List-Id: Don Harrison wrote: > > Matthew Heaney writes: > ... > : > :And as far as your example "proving" that Ada is not type-safe: that is > :incorrect. > > Correct, according to the Ada definition. As Norman Cohen put it, > > : It shows that Ada is not subtype-safe. > > That becomes "not type-safe" if you regard sub-types as distinct types. I'm reminded of the following riddle, which I've seen attributed to Abraham Lincoln: Q: If you call a dog's tail a leg, how many legs does a dog have? A: Four. Calling the tail a leg does not make it one. Calling a subtype a distinct type does not make it one. Reread that post of mine that you quoted. Its main point is that, according to the Ada definition, subtypes are NOT distinct types. Distinct types are disjoint sets of values distinguished at compile time. Subtypes of a type are (possibly overlapping) sets of values in the same type, distinguished by whether or not they obey certain constraints that can, in general, only be checked at run time. -- Norman H. Cohen mailto:ncohen@watson.ibm.com http://www.research.ibm.com/people/n/ncohen