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Re: sscanf question

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Keith Thompson <kst-u@mib.org> wrote:

(snip, someone wrote)
>> Floating point is workable if you know that an amount might be meant to
>> represent a whole number of cents for example. Or you can use floating
>> point to represent cents rather than dollars ...
 
> Floating-point can't exactly represent all integer values within its
> range -- and operations that yield inexact results generally don't give
> any warning about a loss of precision.  If you can guarantee that all
> the numbers you'll be dealing with are within the contiguous range of
> integers that can be represented exactly, then you'll probably be ok.

Also, as long as you don't do division. Well, it will work for a
while, but can fail long before add, subtract, and multiply when the
result is rounded differently than you expect.

Now, with IEEE you know that the result is rounded. 

IBM S/360 (and HFP on newer processors) truncates the quotient
(except on the 360/91 and related processors). The truncated
quotient might be a better choice if you are using it for
integer arithmetic.

> But then why use floating-point rather a large integer type 
> in the first place?

Yes, good question. In the days of 16 bit integers and 64 bit
floating point, I know some used floating point for larger
integer values, but now with 64 bit integers on most machines
there isn't much of an excuse anymore.
 
> For *serious* financial calculations, there are typically standards that
> specify exactly how those calculations are to be carried out.  In such
> contexts, you need to find those standards and follow them.

Yes.

And also, as Knuth says, for typesetting.

-- glen

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sscanf question "Brian O'Brien" <bjobrien62@gmail.com> - 2012-12-12 13:29 -0800
  Re: sscanf question "BartC" <bc@freeuk.com> - 2012-12-12 21:43 +0000
  Re: sscanf question James Kuyper <jameskuyper@verizon.net> - 2012-12-12 16:52 -0500
  Re: sscanf question Les Cargill <lcargill99@comcast.com> - 2012-12-12 22:14 -0600
    Re: sscanf question Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-12-13 14:03 +0000
  Re: sscanf question falk@rahul.net (Edward A. Falk) - 2012-12-13 20:36 +0000
    Re: sscanf question Prathamesh Kulkarni <bilbotheelffriend@gmail.com> - 2012-12-13 13:40 -0800
      Re: sscanf question Fred K <fred.l.kleinschmidt@gmail.com> - 2012-12-13 14:31 -0800
        Re: sscanf question Fred K <fred.l.kleinschmidt@gmail.com> - 2012-12-13 14:33 -0800
          Re: sscanf question "BartC" <bc@freeuk.com> - 2012-12-13 22:51 +0000
            Re: sscanf question Keith Thompson <kst-u@mib.org> - 2012-12-13 15:45 -0800
              Re: sscanf question glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2012-12-14 00:06 +0000
              Re: sscanf question "BartC" <bc@freeuk.com> - 2012-12-14 02:33 +0000
                Re: sscanf question glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2012-12-14 03:25 +0000
                Re: sscanf question "BartC" <bc@freeuk.com> - 2012-12-14 11:50 +0000
                Re: sscanf question glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2012-12-14 12:19 +0000
                Re: sscanf question "BartC" <bc@freeuk.com> - 2012-12-14 13:38 +0000
                Re: sscanf question glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2012-12-14 20:40 +0000
                Re: sscanf question Nick Keighley <nick_keighley_nospam@hotmail.com> - 2012-12-16 03:34 -0800
          Re: sscanf question falk@rahul.net (Edward A. Falk) - 2012-12-15 03:28 +0000
            Re: sscanf question Les Cargill <lcargill99@comcast.com> - 2012-12-14 22:41 -0600
              Re: sscanf question Keith Thompson <kst-u@mib.org> - 2012-12-15 01:25 -0800
                Re: sscanf question glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2012-12-15 10:26 +0000
                Re: sscanf question Les Cargill <lcargill99@comcast.com> - 2012-12-15 13:24 -0600
                Re: sscanf question glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2012-12-15 20:15 +0000
                Re: sscanf question Les Cargill <lcargill99@comcast.com> - 2012-12-15 15:33 -0600
                [OT] Re: sscanf question Eric Sosman <esosman@comcast-dot-net.invalid> - 2012-12-15 17:49 -0500
                Re: [OT] Re: sscanf question glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2012-12-16 00:16 +0000
            Re: sscanf question Barry Schwarz <schwarzb@dqel.com> - 2012-12-14 21:28 -0800
            Re: sscanf question glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2012-12-15 08:17 +0000
      Re: sscanf question Eric Sosman <esosman@comcast-dot-net.invalid> - 2012-12-13 18:22 -0500
  Re: sscanf question "Brian O'Brien" <bjobrien62@gmail.com> - 2012-12-13 21:13 -0800
    Re: sscanf question Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-12-14 12:25 +0000

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