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Re: value of pi and 22/7

From Ethan Furman <ethan@stoneleaf.us>
Newsgroups comp.lang.python
Subject Re: value of pi and 22/7
Date 2016-06-17 19:27 -0700
Message-ID <mailman.110.1466216834.2288.python-list@python.org> (permalink)
References (4 earlier) <91940d31-1ff4-4267-9b07-445eca35d234@googlegroups.com> <CALwzidnqyDKZ=9MBpu9QiF4Lk+MduEmvQ3L9CSknb60kP=zSCA@mail.gmail.com> <mailman.107.1466207356.2288.python-list@python.org> <5764a19c$0$1603$c3e8da3$5496439d@news.astraweb.com> <5764B17C.3080809@stoneleaf.us>

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On 06/17/2016 06:19 PM, Steven D'Aprano wrote:
> On Sat, 18 Jun 2016 09:49 am, Ian Kelly wrote:

>> If I tell you that the speed of light is 300,000,000 m/s, do you think
>> that measurement has 9 significant digits? If you do, then you would be
>> wrong.
>
> Hmmm.
>
> If I tell you that some physical phenomenon [let's call it the speed of
> light] is 299,999,999 m/s, how many significant digits would I be using?

I know!  I know!  9!

> What if I tell you that it's 300,000,001 m/s?

Oh!  9 again!

> What if the figure to nine significant digits *actually is* three followed
> by eight zeroes?

Hmmm... thinking.... thinking... oh yeah!  You put a bar over the last 
significant digit -- or you use scientific notation:

30e7 has two significant digits.

> For all that it is in widespread use, I think the concept of "significant
> figures" is inherently ambiguous.

Not at all -- just have to keep your notations correct*.

--
~Ethan~

* Mine might be 30 years out of date, but maybe not.

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Thread

Re: value of pi and 22/7 Lawrence D’Oliveiro <lawrencedo99@gmail.com> - 2016-06-17 16:12 -0700
  Re: value of pi and 22/7 Ian Kelly <ian.g.kelly@gmail.com> - 2016-06-17 17:49 -0600
    Re: value of pi and 22/7 Steven D'Aprano <steve@pearwood.info> - 2016-06-18 11:19 +1000
      Re: value of pi and 22/7 Ethan Furman <ethan@stoneleaf.us> - 2016-06-17 19:27 -0700
      Re: value of pi and 22/7 Tim Harig <timharig@eternal-september.org> - 2016-06-18 05:47 +0000
        Re: value of pi and 22/7 boB Stepp <robertvstepp@gmail.com> - 2016-06-18 10:22 -0500
      Re: value of pi and 22/7 Christian Gollwitzer <auriocus@gmx.de> - 2016-06-18 09:56 +0200
  Re: value of pi and 22/7 Random832 <random832@fastmail.com> - 2016-06-17 23:48 -0400
    Re: value of pi and 22/7 Lawrence D’Oliveiro <lawrencedo99@gmail.com> - 2016-06-17 21:30 -0700
      Re: value of pi and 22/7 Ian Kelly <ian.g.kelly@gmail.com> - 2016-06-17 23:18 -0600
        Re: value of pi and 22/7 Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2016-06-20 10:25 +1200
          Re: value of pi and 22/7 Steven D'Aprano <steve@pearwood.info> - 2016-06-20 12:07 +1000
            Re: value of pi and 22/7 Grant Edwards <grant.b.edwards@gmail.com> - 2016-06-20 18:06 +0000
          Re: value of pi and 22/7 Ian Kelly <ian.g.kelly@gmail.com> - 2016-06-19 23:19 -0600
            Re: value of pi and 22/7 Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2016-06-20 16:22 +1000
              Re: value of pi and 22/7 Ian Kelly <ian.g.kelly@gmail.com> - 2016-06-20 10:01 -0600
                Re: value of pi and 22/7 Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2016-06-21 18:38 +1000
              Re: value of pi and 22/7 Ian Kelly <ian.g.kelly@gmail.com> - 2016-06-20 10:09 -0600
          Re: value of pi and 22/7 Lawrence D’Oliveiro <lawrencedo99@gmail.com> - 2016-06-19 22:51 -0700
            Re: value of pi and 22/7 Marko Rauhamaa <marko@pacujo.net> - 2016-06-20 10:32 +0300
              Re: value of pi and 22/7 Lawrence D’Oliveiro <lawrencedo99@gmail.com> - 2016-06-20 01:01 -0700
                Re: value of pi and 22/7 Wildman <best_lay@yahoo.com> - 2016-06-20 17:24 -0500
                Re: value of pi and 22/7 Marko Rauhamaa <marko@pacujo.net> - 2016-06-21 01:47 +0300
                Re: value of pi and 22/7 Lawrence D’Oliveiro <lawrencedo99@gmail.com> - 2016-06-22 14:20 -0700
      Re: value of pi and 22/7 Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2016-06-20 10:14 +1200
        Re: value of pi and 22/7 Grant Edwards <grant.b.edwards@gmail.com> - 2016-06-20 17:53 +0000
        Re: value of pi and 22/7 Marko Rauhamaa <marko@pacujo.net> - 2016-06-20 21:52 +0300
          Re: value of pi and 22/7 Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2016-06-22 00:52 +1200
  Re: value of pi and 22/7 Pete Forman <petef4+usenet@gmail.com> - 2016-06-18 13:05 +0100
  Re: value of pi and 22/7 Johannes Bauer <dfnsonfsduifb@gmx.de> - 2016-06-18 18:09 +0200

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