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Re: Exact integer-valued floats

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On 22 Sep 2012 01:36:59 GMT, Steven D'Aprano
<steve+comp.lang.python@pearwood.info> declaimed the following in
gmane.comp.python.general:

> 
> For non IEEE 754 floating point systems, there is no telling how bad the 
> implementation could be :(

	Let's see what can be found...

http://www.bitsavers.org/pdf/sds/sigma/sigma6/901713B_Sigma_6_Reference_Man_Jun71.pdf
pages 50-54
	A sign bit, 7-bit offset base 16 exponent/characteristic, 24-bit
mantissa/fraction (for short; long float is 56 bit mantissa).

	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]).



	Motorola Fast Floating Point (software library for the Amiga, and
apparently also used on early Palm units)
	Sign bit, 7-bit binary exponent, 24-bit mantissa


	VAX http://nssdc.gsfc.nasa.gov/nssdc/formats/VAXFloatingPoint.htm
(really nasty looking as bits 6 is most significant, running down to bit
0, THEN bits 32-16 with 16 the least significant; extend for longer
formats)
	F-float: sign bit,  8-bit exponent, 23 bits mantissa
	D-float: as above but 55 bits mantissa
	G-float: sign bit, 11-bit exponent, 52 bits mantissa
	H-float: sign bit, 15-bit exponent, 112 bits mantissa

-- 
	Wulfraed                 Dennis Lee Bieber         AF6VN
        wlfraed@ix.netcom.com    HTTP://wlfraed.home.netcom.com/

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Thread

Exact integer-valued floats Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-09-21 17:29 +0000
  Re: Exact integer-valued floats Ian Kelly <ian.g.kelly@gmail.com> - 2012-09-21 12:13 -0600
  Re: Exact integer-valued floats Jussi Piitulainen <jpiitula@ling.helsinki.fi> - 2012-09-21 22:47 +0300
  Re: Exact integer-valued floats Nobody <nobody@nowhere.com> - 2012-09-21 20:59 +0100
  Re: Exact integer-valued floats Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2012-09-21 16:26 -0400
    Re: Exact integer-valued floats Hans Mulder <hansmu@xs4all.nl> - 2012-09-21 23:04 +0200
      Re: Exact integer-valued floats Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2012-09-21 20:54 -0400
  Re: Exact integer-valued floats Alister <alister.ware@ntlworld.com> - 2012-09-21 21:14 +0000
  Re: Exact integer-valued floats Paul Rubin <no.email@nospam.invalid> - 2012-09-21 15:23 -0700
    Re: Exact integer-valued floats Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-09-22 01:36 +0000
      Re: Exact integer-valued floats Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2012-09-22 01:01 -0400
        Re: Exact integer-valued floats Tim Roberts <timr@probo.com> - 2012-09-22 14:05 -0700
          Re: Exact integer-valued floats Dave Angel <d@davea.name> - 2012-09-22 19:06 -0400
            Re: Exact integer-valued floats Hans Mulder <hansmu@xs4all.nl> - 2012-09-23 09:45 +0200
          Re: Exact integer-valued floats wrw@mac.com - 2012-09-24 11:29 -0400
    Re: Exact integer-valued floats Nobody <nobody@nowhere.com> - 2012-09-22 11:19 +0100

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