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=-0.3 required=5.0 tests=BAYES_00, REPLYTO_WITHOUT_TO_CC autolearn=no autolearn_force=no version=3.4.4 X-Google-Thread: 103376,24d7acf9b853aac8 X-Google-NewGroupId: yes X-Google-Attributes: gida07f3367d7,domainid0,public,usenet X-Google-Language: ENGLISH,ASCII-7-bit Path: g2news1.google.com!news3.google.com!proxad.net!feeder1-2.proxad.net!newsfeed.straub-nv.de!noris.net!newsfeed.arcor.de!newsspool2.arcor-online.net!news.arcor.de.POSTED!not-for-mail From: "Dmitry A. Kazakov" Subject: Re: S-expression I/O in Ada Newsgroups: comp.lang.ada User-Agent: 40tude_Dialog/2.0.15.1 MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Reply-To: mailbox@dmitry-kazakov.de Organization: cbb software GmbH References: <547afa6b-731e-475f-a7f2-eaefefb25861@k8g2000prh.googlegroups.com> <258zlxrv4fn6.1vszho1rtmf48$.dlg@40tude.net> <984db477-973c-4a66-9bf6-e5348c9b95f2@n19g2000prf.googlegroups.com> <46866b8yq8nn$.151lqiwa0y2k6.dlg@40tude.net> <13b07f2c-2f35-43e0-83c5-1b572c65d323@y11g2000yqm.googlegroups.com> <13tpf7ya3evig$.h05p3x08059s$.dlg@40tude.net> <1omt2srxtpsga$.c3hbxthzo6cf.dlg@40tude.net> <1e4cch2df5uyb.18brqdd16dhv8.dlg@40tude.net> <14y70ke8am9qw$.2csc9eflvigg.dlg@40tude.net> <1y1c8zzqmcer5.po56hkesa968.dlg@40tude.net> Date: Tue, 10 Aug 2010 08:48:11 +0200 Message-ID: <1o6jah15584x1$.1arrrgog9jdk7.dlg@40tude.net> NNTP-Posting-Date: 10 Aug 2010 08:48:10 CEST NNTP-Posting-Host: 941d6210.newsspool4.arcor-online.net X-Trace: DXC==OCPI2GXaLV=>bdbdS?M0Y4IUK On Mon, 9 Aug 2010 20:17:40 -0500, Randy Brukardt wrote: > "Dmitry A. Kazakov" wrote in message > news:1y1c8zzqmcer5.po56hkesa968.dlg@40tude.net... > ... >>> For these, you don't want modular semantics -- you just want >>> a data type whose representation matches what you're >>> interfacing/communicating with, such as "type Octet is >>> range 0..2**8-1;" >> >> The problem is that these things require both array-of-Boolean view and >> arithmetic. I agree that when arithmetic is used, then it has to be wide. >> E.g. when interpreting sequences of octets as little/big endian numbers, >> we >> never use modular arithmetic. But integer arithmetic is incompatible with >> array/set view. > > What have you done with Dmitry?? You can't be the *real* Dmitry! :-) Brainwashed me? (:-)) > Array-of-bytes views and arithmetic views are of clearly different types, > with different sets of operations. These shouldn't be mixed, logically or > any other way. If you need to go between these views, you need some sort of > type conversion (or Unchecked_Conversion or Stream'Read or...). Thus, it is > *never* necessary to do operations on both views at once, and it is > irrelevant what the "math" operations for octets is. If Ada gets anything > wrong about this, it is that it has math operations at all for > stream_elements. Right, but there is no contradiction because it is more than one type involved. What I meant is: type Octet is ...; -- Array interface to access bits of the octet (not Ada) type Bit_Index is range 1..8; function "()" (Unit : Octet; Bit : Bit_Index) return Boolean; procedure "()" (Unit : in out Octet; Bit : Bit_Index; Value : Boolean); -- Arithmetic interface, immediately leads out of octets (not Ada) function "+" (Left, Right : Octet) return Universal_Integer; function "-" (Left, Right : Octet) return Universal_Integer; ... So when you write: Little_Endian_Value := Octet_1 + Octet_2 * 256; There result is not an octet, as it would be with a modular type. Presently it is just broken. -- Regards, Dmitry A. Kazakov http://www.dmitry-kazakov.de