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,e3feb606f668a7c1 X-Google-Attributes: gid103376,public From: "Mike Silva" Subject: Re: Why should hackers love Ada. (Re: Ada 95 based RTOS) Date: 2000/02/25 Message-ID: #1/1 X-Deja-AN: 590018217 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-MIMEOLE: Produced By Microsoft MimeOLE V4.72.3110.3 X-Complaints-To: news@wenet.net X-Trace: news.wenet.net 951513456 206.169.137.33 (Fri, 25 Feb 2000 13:17:36 PST) X-Received-Date: Fri, 25 Feb 2000 13:17:46 PST (newsfeed.avtel.net) NNTP-Posting-Date: Fri, 25 Feb 2000 13:17:36 PST Newsgroups: comp.lang.ada Date: 2000-02-25T00:00:00+00:00 List-Id: 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. Mike