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Re: Floating point "g" format not stripping trailing zeros

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From Ian Kelly <ian.g.kelly@gmail.com>
Date Fri, 13 Feb 2015 09:56:28 -0700
Subject Re: Floating point "g" format not stripping trailing zeros
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On Fri, Feb 13, 2015 at 7:02 AM, Grant Edwards <invalid@invalid.invalid> wrote:
> On 2015-02-12, Ian Kelly <ian.g.kelly@gmail.com> wrote:
>> On Thu, Feb 12, 2015 at 1:23 PM, Hrvoje Nikšić <hniksic@gmail.com> wrote:
>>
>>> {:.15g} is supposed to give 15 digits of precision, but with trailing
>>> zeros removed.
>>
>> The doc says with "insignificant" trailing zeros removed, not all
>> trailing zeros.
>
> Can somebody explain the difference between "significant" and
> "insignificant" tailing zeros to somebody who barely passed his single
> numerical methods class?  [Though I have, on occasion, had to tinker
> with the innards of SW floating point libraries and could fish a
> hardcopy of IEEE-754 out of a filing cabinet if needed.]

Significant digits are within the precision of the calculation.
Writing 1.230 indicates that the fourth digit is known to be zero.
Writing 1.23 outside a context of exact calculation indicates that the
fourth digit is unknown due to insufficient precision.

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Thread

Re: Floating point "g" format not stripping trailing zeros Ian Kelly <ian.g.kelly@gmail.com> - 2015-02-12 16:46 -0700
  Re: Floating point "g" format not stripping trailing zeros Grant Edwards <invalid@invalid.invalid> - 2015-02-13 14:02 +0000
    Re: Floating point "g" format not stripping trailing zeros Ian Kelly <ian.g.kelly@gmail.com> - 2015-02-13 09:56 -0700
      Re: Floating point "g" format not stripping trailing zeros Grant Edwards <invalid@invalid.invalid> - 2015-02-13 20:33 +0000
        Re: Floating point "g" format not stripping trailing zeros Ian Kelly <ian.g.kelly@gmail.com> - 2015-02-13 14:01 -0700
        Re: Floating point "g" format not stripping trailing zeros Dave Angel <davea@davea.name> - 2015-02-13 16:15 -0500
          Re: Floating point "g" format not stripping trailing zeros Grant Edwards <invalid@invalid.invalid> - 2015-02-13 21:22 +0000
            Re: Floating point "g" format not stripping trailing zeros Ian Kelly <ian.g.kelly@gmail.com> - 2015-02-13 14:40 -0700
            Re: Floating point "g" format not stripping trailing zeros Ian Kelly <ian.g.kelly@gmail.com> - 2015-02-13 14:49 -0700

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