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Re: comparing floating point numbers

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On 1/29/12 12:34 PM, Marcel Müller wrote:
> On 29.01.2012 19:48, Adam Majewski wrote:
>> I have seen code that compers like that :
>>
>> if (b == 0.0 && (a == 0.25 || a == -0.75))
>
> Comparing floating point numbers for equality is almost always a bug.
> Only singular values like 0.0 are usually safe.
>
>
> Marcel

Agreed. And anyone who made it past the 1st Intro to CS class would know 
that. I've no idea of the Original Poster's background so I wasn't going 
to speculate on his training. I'm pretty sure english is a 2nd language 
for him so what he asked and what he meant to ask were not quite the 
same. I can't fault someone for that.

But, yes, comparing floats for equality is not a good thing.

-- 
Dave Scruggs

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Thread

comparing floating point numbers Adam Majewski <adammaj1@o2.pl> - 2012-01-29 19:48 +0100
  Re: comparing floating point numbers BCFD36 <bcfd36@cruzio.com> - 2012-01-29 11:02 -0800
    Re: comparing floating point numbers "MikeWhy" <boat042-nospam@yahoo.com> - 2012-01-29 13:25 -0600
      Re: comparing floating point numbers "Alf P. Steinbach" <alf.p.steinbach+usenet@gmail.com> - 2012-01-29 20:40 +0100
    Re: comparing floating point numbers Adam Majewski <adammaj1@o2.pl> - 2012-01-30 18:03 +0100
  Re: comparing floating point numbers Marcel Müller <news.5.maazl@spamgourmet.com> - 2012-01-29 21:34 +0100
    Re: comparing floating point numbers BCFD36 <bcfd36@cruzio.com> - 2012-01-29 14:55 -0800
      Re: comparing floating point numbers Miles Bader <miles@gnu.org> - 2012-01-30 11:48 +0900
        Re: comparing floating point numbers Juha Nieminen <nospam@thanks.invalid> - 2012-01-30 14:53 +0000
    Re: comparing floating point numbers scott@slp53.sl.home (Scott Lurndal) - 2012-01-30 17:22 +0000
      Re: comparing floating point numbers Robert Wessel <robertwessel2@yahoo.com> - 2012-01-30 13:55 -0600
      Re: comparing floating point numbers glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2012-02-13 01:56 +0000
  Re: comparing floating point numbers LR <lruss@superlink.net> - 2012-01-29 18:30 -0500
    Re: comparing floating point numbers Thomas Boell <tboell@domain.invalid> - 2012-01-30 16:29 +0100
  Re: comparing floating point numbers Christian Gollwitzer <auriocus@gmx.de> - 2012-01-30 08:07 +0100
    Re: comparing floating point numbers glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2012-02-13 01:59 +0000
  Re: comparing floating point numbers Nick Keighley <nick_keighley_nospam@hotmail.com> - 2012-01-30 06:26 -0800

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