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: kilgallen@eisner.decus.org (Larry Kilgallen) Subject: Re: Why should hackers love Ada. (Re: Ada 95 based RTOS) Date: 2000/02/24 Message-ID: <2000Feb24.122253.1@eisner>#1/1 X-Deja-AN: 589386497 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> X-Trace: news.decus.org 951412977 10842 KILGALLEN [216.44.122.34] Organization: LJK Software Reply-To: Kilgallen@eisner.decus.org.nospam Newsgroups: comp.lang.ada Date: 2000-02-24T00:00:00+00:00 List-Id: 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.