Path: csiph.com!usenet.pasdenom.info!gegeweb.org!de-l.enfer-du-nord.net!feeder1.enfer-du-nord.net!feeds.phibee-telecom.net!newsfeed.xs4all.nl!newsfeed6.news.xs4all.nl!xs4all!newsgate.cistron.nl!newsgate.news.xs4all.nl!post.news.xs4all.nl!not-for-mail Return-Path: X-Original-To: python-list@python.org Delivered-To: python-list@mail.python.org X-Spam-Status: OK 0.006 X-Spam-Evidence: '*H*': 0.99; '*S*': 0.00; '(at': 0.03; 'float': 0.05; '22,': 0.09; '754': 0.09; 'assumed': 0.09; 'internally': 0.09; 'least)': 0.09; 'sep': 0.09; 'zero.': 0.09; 'dec': 0.15; 'to:name :python-list': 0.15; 'arithmetic.': 0.16; 'ebcdic': 0.16; 'oddity': 0.16; 'polling': 0.16; 'received:mac.com': 0.16; 'set)': 0.16; 'set,': 0.16; 'track.': 0.16; 'vectors': 0.16; 'later': 0.16; 'wrote:': 0.17; 'integer': 0.17; 'received:10.0.1': 0.17; 'tim': 0.18; '>>>': 0.18; 'sort': 0.21; 'bit': 0.21; 'cc:2**0': 0.23; 'to:2**1': 0.23; "i've": 0.23; 'non': 0.24; 'machine': 0.24; '(which': 0.26; 'values': 0.26; 'first.': 0.27; 'ibm': 0.27; '>>>>': 0.29; 'cpu': 0.29; "d'aprano": 0.29; 'steven': 0.29; 'url:mailman': 0.29; 'convert': 0.29; 'words': 0.29; 'worked': 0.30; 'basic': 0.30; 'point': 0.31; 'url:python': 0.32; 'instruction': 0.32; 'could': 0.32; 'url:listinfo': 0.32; 'received:10.0': 0.33; 'to:addr:python-list': 0.33; 'along': 0.35; 'received:17': 0.35; 'pm,': 0.35; 'there': 0.35; 'but': 0.36; 'url:org': 0.36; 'bad': 0.37; 'two': 0.37; 'late': 0.37; 'systems,': 0.37; 'data': 0.37; 'subject:: ': 0.38; 'some': 0.38; 'received:10': 0.38; 'several': 0.39; 'to:addr:python.org': 0.39; 'subject:-': 0.40; 'url:mail': 0.40; 'lost': 0.60; 'from:no real name:2**0': 0.60; 'telling': 0.61; 'series': 0.63; 'different': 0.63; 'charset:windows-1252': 0.65; 'issued': 0.65; 'believe': 0.69; '(they': 0.84; 'forced': 0.84; 'interrupt': 0.84; 'multiply': 0.84; 'dennis': 0.91; '1988': 0.93; 'angel': 0.93; 'incorporated': 0.93; 'remember,': 0.93; 'instrument': 0.95 MIME-version: 1.0 Content-type: text/plain; charset=windows-1252 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:5.7.7855,1.0.431,0.0.0000 definitions=2012-09-24_04:2012-09-24, 2012-09-24, 1970-01-01 signatures=0 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 spamscore=0 ipscore=0 suspectscore=0 phishscore=0 bulkscore=0 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=6.0.2-1203120001 definitions=main-1209240177 Subject: Re: Exact integer-valued floats From: wrw@mac.com In-reply-to: <505E4460.5060301@davea.name> Date: Mon, 24 Sep 2012 11:29:12 -0400 Content-transfer-encoding: quoted-printable References: <505ca3e9$0$29981$c3e8da3$5496439d@news.astraweb.com> <7xzk4j6mmq.fsf@ruckus.brouhaha.com> <505d163b$0$29981$c3e8da3$5496439d@news.astraweb.com> <505E4460.5060301@davea.name> To: d@davea.name, python-list X-Mailer: Apple Mail (2.1498) Cc: "William R. Wing" X-BeenThere: python-list@python.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: General discussion list for the Python programming language List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Newsgroups: comp.lang.python Message-ID: Lines: 53 NNTP-Posting-Host: 2001:888:2000:d::a6 X-Trace: 1348504165 news.xs4all.nl 6932 [2001:888:2000:d::a6]:33789 X-Complaints-To: abuse@xs4all.nl Xref: csiph.com comp.lang.python:29915 On Sep 22, 2012, at 7:06 PM, Dave Angel wrote: > On 09/22/2012 05:05 PM, Tim Roberts wrote: >> Dennis Lee Bieber wrote: >>> On 22 Sep 2012 01:36:59 GMT, Steven D'Aprano wrote: >>>> For non IEEE 754 floating point systems, there is no telling how = bad the=20 >>>> implementation could be :( >>> Let's see what can be found... >>>=20 >>> IBM 360: Same as Sigma-6 (no surprise; hearsay is the Sigma was >>> designed by renegade IBM folk; even down to using EBCDIC internally = -- >>> but with a much different interrupt system [224 individual interrupt >>> vectors as I recall, vs the IBM's 7 vectors and polling to find what >>> device]). >> The Control Data 6000/Cyber series had sign bit and 11-bit exponent, = with >> either a 48-bit mantissa or a 96-bit mantissa, packed into one or two >> 60-bit words. Values were not automatically normalized, so there was = no >> assumed 1 bit, as in IEEE-754. >=20 > And it's been a long time (about 39 years), but as I recall the CDC = 6400 > (at least) had no integer multiply or divide. You had to convert to > float first. The other oddity about the CDC series is it's the last > machine I've encountered that used ones-complement for ints, with two > values for zero. >=20 >=20 Well, for what it is worth=85 the DEC Laboratory INstrument Computer = (LINC-8, sort of a forced acronym because I believe they were built to = specs issued by Lincoln Labs.) and the later DEC PDP-12 (which = incorporated the LINC-8 instruction set, along with the PDP-8 basic set) = also did ones-complement integer arithmetic. I never used a LINC-8, but = I worked for several years around PDP-12s. (They also had a build-in = CRT and a MUX'd analog-to-digital converter with CPU instructions for = driving both directly.) As I remember, they maxed out at 32k (12-bit) = words of RAM. I don't know when they were discontinued, but there were = still some PDP-12s in use as late as 1988 when I lost track.=20 -Bil > --=20 >=20 > DaveA >=20 > --=20 > http://mail.python.org/mailman/listinfo/python-list