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: 103376,e3feb606f668a7c1 X-Google-Attributes: gid103376,public From: Gary Scott Subject: Re: Why should hackers love Ada. (Re: Ada 95 based RTOS) Date: 2000/02/26 Message-ID: <38B80D45.B1EDDC69@flash.net>#1/1 X-Deja-AN: 590313535 Content-Transfer-Encoding: 7bit References: <88ilp7$bcm$1@nnrp1.deja.com> <38ADCA44.3B91BF6F@averstar.com> <88qli0$gvr$1@nnrp1.deja.com> <38B2A2A1.FDCDDFE7@honeywell.com> <88ugrd$7j7$1@nnrp1.deja.com> <890ght$bih1@ftp.kvaerner.com> <38B3EA94.E3AB4929@maths.unine.ch> <38B41432.88D7389F@quadruscorp.com> <38B47521.1A80B6A1@lmtas.lmco.com> <38B55928.8A0EAB06@quadruscorp.com> <2000Feb24.122253.1@eisner> <38B5C9E6.143A32D6@flash.net> X-Accept-Language: en Content-Type: text/plain; charset=us-ascii X-Complaints-To: abuse@flash.net X-Trace: news.flash.net 951586072 216.215.83.128 (Sat, 26 Feb 2000 11:27:52 CST) Organization: Home MIME-Version: 1.0 Reply-To: scottg@flash.net NNTP-Posting-Date: Sat, 26 Feb 2000 11:27:52 CST Newsgroups: comp.lang.ada Date: 2000-02-26T00:00:00+00:00 List-Id: Mike Silva wrote: > Gary Scott wrote in message <38B5C9E6.143A32D6@flash.net>... > >Larry Kilgallen wrote: > > > >> In article <38B55928.8A0EAB06@quadruscorp.com>, "Marin D. Condic" > writes: > >> > Gary wrote: > >> >> I see this reference to ADA being good at bit twiddling, periodically. > >> >> Virtually all high-level languages provide facilities for bit > twiddling. Is > >> >> there something unique about ADA (I'm a non-ADA programmers, sorry). > Is this > >> >> a reference to a transfer function (other languages have this) or > memory > >> >> aliasing tricks? > >> > > >> > Well, I don't know what the rest of the world means by "bit twiddling" > >> > but I know what *I* mean when I say that. ;-) > >> > > >> > You have all the facilities you need in Ada (Ada95 - Ada83 didn't do > >> > this well) to do shifting, masking & other manipulations of individual > >> > bits within words. If you've ever had to do interfacing to low level > >> > devices, hardware registers, I/O ports, etc., then you know that you > >> > can't always deal with data as an "abstraction" where you can allow the > >> > compiler to pick whatever representations it wants and manipulate > things > >> > any way it likes. Often I have been up against time constraints where > >> > even if a high level method of solving the problem may work fine, we > >> > dipped into bit masks and logical operators because they degenerated to > >> > much more efficient code. > >> > > >> > Ada95 lets you get at things like this when you need to. The difference > >> > between Ada and C on this issue is that with Ada it is a "last resort" > >> > whereas with C it is a "way of life". (Look at how lots of bindings to > C > >> > stuff includes numeric constants for specifying options by or'ing > >> > together the constants. While Ada can do that, it isn't the usual > >> > idiom.) > >> > >> I think a major advantage of Ada is that it lets the programmer deal > >> at a higher level for the main body of the program, while only the > >> interface description contains the specification that bits 2-4 are > >> treated as a numeric field for the unit number. The compiler aids > >> and enforces adherence to that specification without requiring the > >> programmer to be constantly thinking about it and getting it right. > > > >This is a good feature, but many other languages have similar features > (some very old like Jovial and PL/1). > >In other languages, my experience is that you simply define > pack/unpack/scale routines and write the main > >executive and high-level functionality in a high-level fashion (possibly > OO) and simply invoke these low-level > >"reformat" routines at the top and bottom of the frame (or as-required). > Then again, I'm also used to being > >able to embed assembly to gain access to an interval timer or generate an > interrupt right into the high-level > >language code. > > It seems that you are challenging the group to prove that Ada is somehow > "the best" at "bit-twiddling". I suspect that the only claim that can be > made is that Ada has very good support for such things -- not only > bit-twiddling but also e.g. specification of data representations, tasking > and interrupt handling. Ada is simply a very nice general purpose language > that has everything you need for cuddling up to the hardware. :-) I wasn't really challenging the group to prove Ada's worth, I'm just an interested non-ADA programmer. My company uses Ada 83 extensively and has had significant difficulty meeting memory footprint and code execution performance criteria. I believe this to be mostly the result of poor management decisions regarding forced use of OO in inappropriate ways (yes I know its Ada 83, not Ada 95). I'm really just interested in understanding better the reasons for these difficulties. > > > Mike -- Gary Scott mailto:scottg@flash.net mailto:webmaster@fortranlib.com http://www.fortranlib.com