From -4989161463922708213 X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: f78e5,27b216646bf2abb1 X-Google-Attributes: gidf78e5,public X-Google-ArrivalTime: 1991-03-14 11:44:19 PST Path: gmdzi!unido!mcsun!uunet!pdn!tscs!tct!chip From: chip@tct.uucp (Chip Salzenberg) Newsgroups: comp.std.c++ Subject: Re: Conversions to/from void*, redux Keywords: Sun, C++ Message-ID: <27E01998.6483@tct.uucp> Date: 15 Mar 91 00:47:19 GMT References: <27D5708A.29CF@tct.uucp> <3568@ux.acs.umn.edu> <71210@microsoft.UUCP> Organization: Teltronics/TCT, Sarasota, FL Lines: 34 According to jimad@microsoft.UUCP (Jim ADCOCK): >I claim C++ *ought to* allow such implementations [that distinguish >between primitive types and user-defined types]. Such implementations >could be interesting *at least* on lisp-machines, Rekursiv-like "OO" >architectures, and on risc machines with 48-bit pointers. Agreed on the "interesting" count, except for the last: RISC machines are quite well cared for by the current language definition. I must admit that it is not until now that I realize the purpose of Jim's statements. He does not speak to what C++ *is* (the subject on which I have concentrated), but of what it *should be* (in his opinion, of course). I apologize to all readers, especially Jim, for previous articles which may have been unnecessarily critical due to my not having grasped this point. >On at least some such machines, the tagged pointers might have 48-bit >representations, the primitive pointers have 32-bit representations. >The 48-bit pointers would be type-tag + ram-address, whereas the 32-bit >pointers would be ram-address only. Thus conversion from class X* to >char* [for example] really would represent loss of information ... Ah, a concrete example! Thank you; it is quite helpful. It sounds very interesting, too, with a lot of potential for error checking, among other things. I'll keep it in mind. >Should the C++ language be specified in such a way so as to prohibit, >for all time, any such implementations/CPUs ??? It is a truism that no language can be all things to all people. -- Chip Salzenberg at Teltronics/TCT , "Most of my code is written by myself. That is why so little gets done." -- Herman "HLLs will never fly" Rubin