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: 109fba,b87849933931bc93 X-Google-Attributes: gid109fba,public X-Google-Thread: fac41,b87849933931bc93 X-Google-Attributes: gidfac41,public X-Google-Thread: 103376,b87849933931bc93 X-Google-Attributes: gid103376,public X-Google-Thread: f43e6,b87849933931bc93 X-Google-Attributes: gidf43e6,public X-Google-Thread: 1108a1,b87849933931bc93 X-Google-Attributes: gid1108a1,public X-Google-Thread: 114809,b87849933931bc93 X-Google-Attributes: gid114809,public From: Ken Garlington Subject: Re: OO, C++, and something much better! Date: 1997/01/16 Message-ID: <32DE3E90.4A9@lmtas.lmco.com>#1/1 X-Deja-AN: 210604907 references: <32DA822A.2FD8@lmtas.lmco.com> content-type: text/plain; charset=us-ascii organization: Lockheed Martin Tactical Aircraft Systems mime-version: 1.0 newsgroups: comp.lang.c++,comp.lang.smalltalk,comp.lang.eiffel,comp.lang.ada,comp.object,comp.software-eng x-mailer: Mozilla 3.01 (Win95; U) Date: 1997-01-16T00:00:00+00:00 List-Id: Keith Thompson wrote: > > In dewar@merv.cs.nyu.edu (Robert Dewar) writes: > > Ken Garlington wrote > > > > " type My_Integer is new Integer; > > function To_Int is new Unchecked_Conversion ( My_Integer, Integer );" > > > > > > Why on earth use an unchecked conversion here when a perfectly ordinary, > > and completely safe type conversion will work just fine? > > 1. I think it was meant to be a simple example of what you can do > Ada.Unchecked_Conversion, not a useful program. > > 2. A simple conversion wouldn't work; you can't assign to a conversion > (unless passing it as an "out" or "in out" parameter is considered > assignment). > > 3. Actually, Unchecked_Conversion won't work either; an earlier version > of GNAT incorrectly allowed assignment to an Unchecked_Conversion. As do various Ada83 compilers (which is why I tried it in the first place!) > If you really want a writable view of an object with a type other than the > object's declared type, you can use 'Access and Unchecked_Conversion on > access types, though it's generally simpler to do an Unchecked_Conversion > on the type itself in the opposite direction. Be careful; it's really > easy to get erroneous execution this way. > > -- > Keith Thompson (The_Other_Keith) kst@aonix.com <*> > TeleSo^H^H^H^H^H^H Alsy^H^H^H^H Thomson Softw^H^H^H^H^H^H^H^H^H^H^H^H^H Aonix > 10251 Vista Sorrento Parkway, Suite 300, San Diego, CA, USA, 92121-2706 > "SPOON!" -- The Tick -- LMTAS - The Fighter Enterprise - "Our Brand Means Quality" For job listings, other info: http://www.lmtas.com or http://www.lmco.com