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Re: Serious error in int() function?

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On 13/04/2016 08:41, martin.spichty@gmail.com wrote:
> Hi,
> 
> there may be a serious error in python's int() function:
> 
> print int(float(2.8/0.1))
> 
> yields
> 
> 27
> 
> instead of 28!!
> 
> I am using Python Python 2.7.6, GCC 4.8.2 on Linux Ubuntu.
> 
> Is that known?

This arises because finite floating point arithmetic is not exact so
2.8/0.1 results in 27.999999999999996.  And, since the int() function
truncates towards zero, this results in a value of 27.

If you want the nearest integer you should use round(x) rather than int(x).

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Serious error in int() function? martin.spichty@gmail.com - 2016-04-13 00:41 -0700
  Re: Serious error in int() function? Marko Rauhamaa <marko@pacujo.net> - 2016-04-13 10:55 +0300
  Re: Serious error in int() function? Alain Ketterlin <alain@universite-de-strasbourg.fr.invalid> - 2016-04-13 10:00 +0200
  Re: Serious error in int() function? Peter Otten <__peter__@web.de> - 2016-04-13 10:03 +0200
  Re: Serious error in int() function? blindanagram@nowhere.net - 2016-04-13 09:04 +0100
  Re: Serious error in int() function? Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2016-04-13 23:51 +1200
  Re: Serious error in int() function? "ast" <nomail@com.invalid> - 2016-04-14 08:52 +0200
    Re: Serious error in int() function? Christian Gollwitzer <auriocus@gmx.de> - 2016-04-14 09:25 +0200
    Accuracy of math.sqrt(), was Re: Serious error in int() function? Peter Otten <__peter__@web.de> - 2016-04-14 09:46 +0200
    Re: Serious error in int() function? blindanagram@nowhere.net - 2016-04-14 08:59 +0100
      Re: Serious error in int() function? blindanagram@nowhere.net - 2016-04-14 09:13 +0100
        Re: Serious error in int() function? blindanagram@nowhere.net - 2016-04-14 13:07 +0100
          Re: Serious error in int() function? Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2016-04-14 20:36 -0400
            Re: Serious error in int() function? Christian Gollwitzer <auriocus@gmx.de> - 2016-04-15 04:38 +0200
              Re: Serious error in int() function? John Pote <johnhpote@o2.co.uk> - 2016-04-15 12:05 +0100
                Re: Serious error in int() function? alister <alister.ware@ntlworld.com> - 2016-04-15 11:50 +0000
            Re: Serious error in int() function? blindanagram@nowhere.net - 2016-04-15 09:41 +0100
              Re: Serious error in int() function? blindanagram@nowhere.net - 2016-04-15 09:41 +0100

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