Path: csiph.com!weretis.net!feeder6.news.weretis.net!news.misty.com!news.iecc.com!.POSTED.news.iecc.com!nerds-end From: anton@mips.complang.tuwien.ac.at (Anton Ertl) Newsgroups: comp.compilers Subject: Re: C arithmetic, was Software proofs, was Are there different Date: Wed, 08 Feb 2023 10:19:54 GMT Organization: Institut fuer Computersprachen, Technische Universitaet Wien Sender: johnl@iecc.com Approved: comp.compilers@iecc.com Message-ID: <23-02-033@comp.compilers> References: <23-01-092@comp.compilers> <23-02-003@comp.compilers> <23-02-019@comp.compilers> <23-02-025@comp.compilers> <23-02-026@comp.compilers> <23-02-029@comp.compilers> Injection-Info: gal.iecc.com; posting-host="news.iecc.com:2001:470:1f07:1126:0:676f:7373:6970"; logging-data="11788"; mail-complaints-to="abuse@iecc.com" Keywords: arithmetic, comment Posted-Date: 08 Feb 2023 11:49:47 EST X-submission-address: compilers@iecc.com X-moderator-address: compilers-request@iecc.com X-FAQ-and-archives: http://compilers.iecc.com Xref: csiph.com comp.compilers:3374 Hans-Peter Diettrich writes: >AFAIK use IEEE-754 floating point numbers still sign-magnitude >representation. >Then the same representation of integral numbers may have advantages in >computations. Such as? Anyway, whatever these advantages may be, they have not been enough to prevent the extermination of sign-magnitude integers. >[I presume the sign-magnitude is to enable the hidden bit trick, >which doesn't apply in unscaled integers. -John] With a ones-complement or two's-complement mantissa the hidden bit would just have the same sign as the sign bit, so this trick is not tied to sign-magnitude representation. Some years ago someone sketched a two's-complement representation for FP (that also includes the exponent), but I did not quite get the details. Anyway, I expect that whatever the advantages of that representation are, they are not enough to justify the transition cost. - anton -- M. Anton Ertl anton@mips.complang.tuwien.ac.at http://www.complang.tuwien.ac.at/anton/ [PDP-6/10 floating point was two's complement. As someone else recently noted, that meant they could use fixed point compare instructions. -John]