Re: Can this program be improved?

From	Kaz Kylheku <480-992-1380@kylheku.com>
Newsgroups	comp.lang.c
Subject	Re: Can this program be improved?
Date	2021-12-30 00:34 +0000
Organization	A noiseless patient Spider
Message-ID	<20211229162959.990@kylheku.com> (permalink)
References	(2 earlier) <sqi3p9$1bia$1@gioia.aioe.org> <sqi72e$q7e$1@dont-email.me> <87sfub2g2t.fsf@nosuchdomain.example.com> <sqiprq$1kk$1@dont-email.me> <Cy6zJ.242630$IW4.143221@fx48.iad>

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On 2021-12-29, Scott Lurndal <scott@slp53.sl.home> wrote:
> Bart <bc@freeuk.com> writes:
>>On 29/12/2021 22:37, Keith Thompson wrote:
>>> Bart <bc@freeuk.com> writes:
>>> [...]
>>>> 3) Double is perfectly suitable for representing monetary amounts,
>>>> especially in a toy program or for personal use. (I've used it for
>>>> accounts within a small business.)
>>> 
>>> In a toy program, sure -- and I'd say *only* in a toy program.
>>> 
>>> Using floating-point for money risks, at best, rare off-by-one errors,
>>> such as a computation yielding a result one cent off from the correct
>>> value.  I believe that would be considered unacceptable in any
>>> real-world financial application.
>>
>>Real-world doesn't need to mean dealing with trillions of dollars to the 
>>exact cent.
>
> Real-world still uses COBOL for these type of applications.
>
>>
>>Most businesses work with amounts far smaller. Then I believe the 
>>precision of float64 is enough to emulate the needed rounding methods.
>
> Why bother with the error-prone "needed rounding methods".  Use uint64_t
> and denominate in mills.

This common intution is incorrect. Financial systems sometimews need to
calculate fractional amounts, like a 15.03% tax or whatever.

And in those situations, you may be required to implement the required
rounding rules: what to do when some fractional result lands halfway
between two pennies: which one does it go to.

You cannot get away from rounding issues just because you used an
integer representation for mills or penies.

-- 
TXR Programming Language: http://nongnu.org/txr
Cygnal: Cygwin Native Application Library: http://kylheku.com/cygnal

Thread

Can this program be improved? Manu Raju <MR@invalid.invalid> - 2021-12-25 01:00 +0000
  Re: Can this program be improved? Andrey Tarasevich <andreytarasevich@hotmail.com> - 2021-12-24 21:44 -0800
    Re: Can this program be improved? David Brown <david.brown@hesbynett.no> - 2021-12-25 12:56 +0100
    Re: Can this program be improved? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2021-12-25 11:13 -0800
    Re: Can this program be improved? Manfred <noname@add.invalid> - 2021-12-25 23:50 +0100
    Re: Can this program be improved? Manu Raju <MR@invalid.invalid> - 2021-12-26 18:52 +0000
      Re: Can this program be improved? Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2021-12-26 19:22 +0000
        Re: Can this program be improved? Manu Raju <MR@invalid.invalid> - 2021-12-26 21:30 +0000
          Re: Can this program be improved? Bart <bc@freeuk.com> - 2021-12-26 22:02 +0000
          Re: Can this program be improved? Richard Damon <Richard@Damon-Family.org> - 2021-12-26 18:24 -0500
          Re: Can this program be improved? Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2021-12-27 00:47 +0000
    Re: Can this program be improved? Guillaume <message@bottle.org> - 2021-12-29 17:52 +0100
      Re: Can this program be improved? Bart <bc@freeuk.com> - 2021-12-29 17:49 +0000
        Re: Can this program be improved? Andrey Tarasevich <andreytarasevich@hotmail.com> - 2021-12-29 11:33 -0800
          Re: Can this program be improved? James Kuyper <jameskuyper@alumni.caltech.edu> - 2021-12-29 22:45 -0500
            Re: Can this program be improved? Andrey Tarasevich <andreytarasevich@hotmail.com> - 2021-12-30 00:35 -0800
              Re: Can this program be improved? David Brown <david.brown@hesbynett.no> - 2021-12-30 10:19 +0100
          Re: Can this program be improved? Bart <bc@freeuk.com> - 2022-01-01 18:19 +0000
            Re: Can this program be improved? Bart <bc@freeuk.com> - 2022-01-01 19:33 +0000
        Re: Can this program be improved? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2021-12-29 14:37 -0800
          Re: Can this program be improved? Bart <bc@freeuk.com> - 2021-12-29 23:09 +0000
            Re: Can this program be improved? scott@slp53.sl.home (Scott Lurndal) - 2021-12-29 23:54 +0000
              Re: Can this program be improved? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2021-12-29 16:11 -0800
              Re: Can this program be improved? Kaz Kylheku <480-992-1380@kylheku.com> - 2021-12-30 00:34 +0000
                Re: Can this program be improved? Bart <bc@freeuk.com> - 2021-12-30 12:49 +0000
                Re: Can this program be improved? Kaz Kylheku <480-992-1380@kylheku.com> - 2021-12-30 21:04 +0000
                Re: Can this program be improved? Bart <bc@freeuk.com> - 2021-12-31 02:13 +0000
            Re: Can this program be improved? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2021-12-29 16:09 -0800
              Re: Can this program be improved? Kaz Kylheku <480-992-1380@kylheku.com> - 2021-12-30 00:59 +0000
                Re: Can this program be improved? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2021-12-29 17:48 -0800
                Re: Can this program be improved? Kaz Kylheku <480-992-1380@kylheku.com> - 2021-12-30 20:47 +0000
              Re: Can this program be improved? Bart <bc@freeuk.com> - 2021-12-30 01:06 +0000
                Re: Can this program be improved? Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2021-12-30 04:48 -0800
                Re: Can this program be improved? Manfred <noname@add.invalid> - 2021-12-30 18:16 +0100
                Re: Can this program be improved? Bart <bc@freeuk.com> - 2021-12-31 02:20 +0000
                Re: Can this program be improved? Manfred <noname@add.invalid> - 2021-12-31 18:25 +0100
                Re: Can this program be improved? James Kuyper <jameskuyper@alumni.caltech.edu> - 2021-12-31 18:13 -0500
                Re: Can this program be improved? Bart <bc@freeuk.com> - 2021-12-31 23:59 +0000
                Re: Can this program be improved? "james...@alumni.caltech.edu" <jameskuyper@alumni.caltech.edu> - 2021-12-31 16:20 -0800
                Re: Can this program be improved? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2021-12-31 16:35 -0800
                Re: Can this program be improved? Bart <bc@freeuk.com> - 2022-01-01 00:53 +0000
                Re: Can this program be improved? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2021-12-31 20:22 -0800
                Re: Can this program be improved? Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2021-12-31 22:04 -0800
                Re: Can this program be improved? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2022-01-01 14:59 -0800
                Re: Can this program be improved? Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2022-01-02 17:22 -0800
                Re: Can this program be improved? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2022-01-02 20:49 -0800
                Re: Can this program be improved? Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2022-01-03 03:09 -0800
                Re: Can this program be improved? scott@slp53.sl.home (Scott Lurndal) - 2022-01-03 16:22 +0000
                Re: Can this program be improved? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2022-01-03 14:42 -0800
                Re: Can this program be improved? Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2022-01-03 14:52 -0800
                Re: Can this program be improved? gazelle@shell.xmission.com (Kenny McCormack) - 2022-01-03 22:58 +0000
                Re: Can this program be improved? Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2022-01-04 04:27 -0800
                Re: Can this program be improved? gazelle@shell.xmission.com (Kenny McCormack) - 2022-01-04 13:39 +0000
                Re: Can this program be improved? David Brown <david.brown@hesbynett.no> - 2022-01-04 00:18 +0100
                Re: Can this program be improved? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2022-01-03 15:24 -0800
                Re: Can this program be improved? Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2022-01-03 15:43 -0800
                Re: Can this program be improved? Öö Tiib <ootiib@hot.ee> - 2022-01-03 21:19 -0800
                Re: Can this program be improved? Mateusz Viste <mateusz@xyz.invalid> - 2022-01-04 09:23 +0100
                Re: Can this program be improved? Guillaume <message@bottle.org> - 2022-01-04 18:18 +0100
                Re: Can this program be improved? Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2022-01-04 10:35 -0800
                Re: Can this program be improved? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2022-01-04 14:07 -0800
                Re: Can this program be improved? Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2022-01-04 15:11 -0800
                Re: Can this program be improved? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2022-01-04 15:47 -0800
                Re: Can this program be improved? Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2022-01-04 18:30 -0800
                Re: Can this program be improved? scott@slp53.sl.home (Scott Lurndal) - 2022-01-04 23:46 +0000
                Re: Can this program be improved? Bart <bc@freeuk.com> - 2022-01-04 18:41 +0000
                Re: Can this program be improved? Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2022-01-04 10:52 -0800
                Re: Can this program be improved? scott@slp53.sl.home (Scott Lurndal) - 2022-01-04 19:00 +0000
                Re: Can this program be improved? Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2022-01-04 11:15 -0800
                Re: Can this program be improved? Guillaume <message@bottle.org> - 2022-01-04 21:57 +0100
                Re: Can this program be improved? Bart <bc@freeuk.com> - 2022-01-04 21:02 +0000
                Re: Can this program be improved? scott@slp53.sl.home (Scott Lurndal) - 2022-01-04 21:38 +0000
                Re: Can this program be improved? Manfred <noname@add.invalid> - 2022-01-04 23:01 +0100
                Re: Can this program be improved? David Brown <david.brown@hesbynett.no> - 2022-01-04 09:31 +0100
                Re: Can this program be improved? Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2022-01-04 01:30 -0800
                Re: Can this program be improved? David Brown <david.brown@hesbynett.no> - 2022-01-04 14:55 +0100
                Re: Can this program be improved? Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2022-01-04 06:21 -0800
                Re: Can this program be improved? David Brown <david.brown@hesbynett.no> - 2022-01-04 16:49 +0100
                Re: Can this program be improved? gazelle@shell.xmission.com (Kenny McCormack) - 2022-01-04 15:56 +0000
                Re: Can this program be improved? gazelle@shell.xmission.com (Kenny McCormack) - 2022-01-04 15:03 +0000
                Re: Can this program be improved? gazelle@shell.xmission.com (Kenny McCormack) - 2022-01-03 22:54 +0000
                Re: Can this program be improved? Mateusz Viste <mateusz@xyz.invalid> - 2022-01-03 09:22 +0100
                Re: Can this program be improved? Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2022-01-03 03:30 -0800
                Re: Can this program be improved? David Brown <david.brown@hesbynett.no> - 2022-01-03 17:22 +0100
                Re: Can this program be improved? Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2022-01-03 08:48 -0800
                Re: Can this program be improved? Mateusz Viste <mateusz@xyz.invalid> - 2022-01-03 18:42 +0100
                Re: Can this program be improved? Bart <bc@freeuk.com> - 2022-01-03 17:59 +0000
                Re: Can this program be improved? Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2022-01-03 11:09 -0800
                Re: Can this program be improved? Mateusz Viste <mateusz@xyz.invalid> - 2022-01-03 20:32 +0100
                Re: Can this program be improved? Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2022-01-03 11:58 -0800
                Re: Can this program be improved? scott@slp53.sl.home (Scott Lurndal) - 2022-01-03 18:13 +0000
                Re: Can this program be improved? gazelle@shell.xmission.com (Kenny McCormack) - 2022-01-03 20:05 +0000
                Re: Can this program be improved? Bart <bc@freeuk.com> - 2022-01-01 16:53 +0000
          Re: Can this program be improved? Kaz Kylheku <480-992-1380@kylheku.com> - 2021-12-30 00:29 +0000
  Re: Can this program be improved? Bart <bc@freeuk.com> - 2021-12-25 12:47 +0000
    Re: Can this program be improved? Manu Raju <MR@invalid.invalid> - 2021-12-26 18:56 +0000
  Re: Can this program be improved? Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2021-12-25 17:38 +0000
    Re: Can this program be improved? Öö Tiib <ootiib@hot.ee> - 2021-12-25 10:58 -0800
      Re: Can this program be improved? Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2021-12-25 19:16 +0000
        Re: Can this program be improved? Öö Tiib <ootiib@hot.ee> - 2021-12-25 11:25 -0800
      Re: Can this program be improved? "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2021-12-25 15:01 -0800
        Re: Can this program be improved? Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2021-12-25 23:09 +0000
          Re: Can this program be improved? "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2021-12-25 20:56 -0800
    Re: Can this program be improved? scott@slp53.sl.home (Scott Lurndal) - 2021-12-25 19:30 +0000
      Re: Can this program be improved? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2021-12-25 15:50 -0800
        Re: Can this program be improved? Manu Raju <MR@invalid.invalid> - 2021-12-26 19:02 +0000
    Re: Can this program be improved? Andrey Tarasevich <andreytarasevich@hotmail.com> - 2021-12-25 11:53 -0800
    Re: Can this program be improved? Manu Raju <MR@invalid.invalid> - 2021-12-26 19:00 +0000
  Re: Can this program be improved? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2021-12-25 11:22 -0800
    Re: Can this program be improved? Manu Raju <MR@invalid.invalid> - 2021-12-26 19:01 +0000
  Re: Can this program be improved? Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2021-12-25 13:27 -0800
    Re: Can this program be improved? Andrey Tarasevich <andreytarasevich@hotmail.com> - 2021-12-25 16:06 -0800
  Re: Can this program be improved? Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2021-12-29 15:21 +0000

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