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Re: Fixed-point arithmetic library

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On Thu, 23 Feb 2012 21:21:31 +0000, Tom Anderson
<twic@urchin.earth.li> wrote:

>On Thu, 23 Feb 2012, Martin Gregorie wrote:
>
>> The only fixed decimal arithmetic I've done in anger was in Cobol, which 
>> will merrily do the following (Identification and Environment divisions 
>> omitted for brevity).

[snipped COBOL code]

>> This would display
>>
>> "     0.800000 /      2.000000 = 0.000000 REMAINDER 0.800000"
>>
>> because, of course, it is exactly equivalent to dividing 800000 by
>> 2000000 and then adding decimal points in their correct fixed positions.
>
>... right. Yes, this is indeed not great. But i don't think this is a 

     If you need exact decimal representation, it is good.

>correct implementation of fixed-point; what you actually have here is 
>essentially integers which are being printed with a format with dots in, 
>right? A fixed-point implementation of multiplication or division needs to 

     Well, yes, that is about what fixed-point is.  Certainly, it is a
common implementation of it.

>do some scaling to get the right answers.

     COBOL handles the scaling automatically.

>> Is that what you want or is BigDecimal doing the right thing for your 
>> problem space?
>
>I don't want what the COBOL does. I need to be able to divide by 2.

     You can do that with COBOL.  Why do you think that you can not?

Sincerely,

Gene Wirchenko

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Fixed-point arithmetic library Tom Anderson <twic@urchin.earth.li> - 2012-02-22 21:39 +0000
  Re: Fixed-point arithmetic library Jan Burse <janburse@fastmail.fm> - 2012-02-22 22:59 +0100
    Re: Fixed-point arithmetic library Tom Anderson <twic@urchin.earth.li> - 2012-02-23 21:15 +0000
      Re: Fixed-point arithmetic library markspace <-@.> - 2012-02-23 13:53 -0800
      Re: Fixed-point arithmetic library Robert Klemme <shortcutter@googlemail.com> - 2012-02-23 23:21 +0100
      Re: Fixed-point arithmetic library Jan Burse <janburse@fastmail.fm> - 2012-02-24 00:02 +0100
  Re: Fixed-point arithmetic library Robert Klemme <shortcutter@googlemail.com> - 2012-02-22 23:13 +0100
    Re: Fixed-point arithmetic library Gene Wirchenko <genew@ocis.net> - 2012-02-22 14:59 -0800
      Re: Fixed-point arithmetic library Martin Gregorie <martin@address-in-sig.invalid> - 2012-02-23 01:05 +0000
        Re: Fixed-point arithmetic library Tom Anderson <twic@urchin.earth.li> - 2012-02-23 21:21 +0000
          Re: Fixed-point arithmetic library Gene Wirchenko <genew@ocis.net> - 2012-02-23 13:49 -0800
      Re: Fixed-point arithmetic library Tom Anderson <twic@urchin.earth.li> - 2012-02-23 21:16 +0000
        Re: Fixed-point arithmetic library Gene Wirchenko <genew@ocis.net> - 2012-02-23 14:03 -0800
          Re: Fixed-point arithmetic library Lew <noone@lewscanon.com> - 2012-02-23 14:42 -0800
            Re: Fixed-point arithmetic library Gene Wirchenko <genew@ocis.net> - 2012-02-23 15:08 -0800
        Re: Fixed-point arithmetic library Martin Gregorie <martin@address-in-sig.invalid> - 2012-02-23 23:05 +0000
    Re: Fixed-point arithmetic library glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2012-02-27 00:59 +0000
      Re: Fixed-point arithmetic library Arne Vajhøj <arne@vajhoej.dk> - 2012-02-26 20:50 -0500
        Re: Fixed-point arithmetic library Robert Klemme <shortcutter@googlemail.com> - 2012-02-27 07:32 +0100
          Re: Fixed-point arithmetic library Jan Burse <janburse@fastmail.fm> - 2012-02-27 13:46 +0100
  Re: Fixed-point arithmetic library Roedy Green <see_website@mindprod.com.invalid> - 2012-02-24 16:26 -0800

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