[issue7704] Math calculation problem (1.6-1.0)>0.6, python said TRUE

[pedro flores]

pedro flores <pflores82 at gmail.com> added the comment:

kk, then i cannot use this comparison?, and this not happen
with....8.6-8>0.6 this is false, according to python.

2010/1/14 Mark Dickinson <report at bugs.python.org>

>
> Mark Dickinson <dickinsm at gmail.com> added the comment:
>
> This is not a bug:  Python, like many other computer languages, stores
> floats in binary.  The values 1.6 and 0.6 aren't exactly representable in
> the internal format used, so the stored versions of 1.6 and 0.6 are actually
> just very close approximations to those values.  It just so happens that the
> approximation for 1.6 is a tiny amount larger than 1.6 (the exact value
> stored is 1.600000000000000088817841970012523233890533447265625), while the
> approximation for 0.6 is a tiny amount smaller than 0.6 (the exact value is
> 0.59999999999999997779553950749686919152736663818359375).
>
> I recommend looking at the appendix to the Python tutorial for more
> information about floating point:
>
> http://docs.python.org/tutorial/floatingpoint.html
>
> ----------
> nosy: +mark.dickinson
> resolution:  -> invalid
> status: open -> closed
>
> _______________________________________
> Python tracker <report at bugs.python.org>
> <http://bugs.python.org/issue7704>
> _______________________________________
>

----------
Added file: http://bugs.python.org/file15884/unnamed

_______________________________________
Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue7704>
_______________________________________
-------------- next part --------------
kk, then i cannot use this comparison?, and this not happen with....8.6-8&gt;0.6 this is false, according to python.<br><br><div class="gmail_quote">2010/1/14 Mark Dickinson <span dir="ltr">&lt;<a href="mailto:report at bugs.python.org">report at bugs.python.org</a>&gt;</span><br>
<blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;"><br>
Mark Dickinson &lt;<a href="mailto:dickinsm at gmail.com">dickinsm at gmail.com</a>&gt; added the comment:<br>
<br>
This is not a bug: Â Python, like many other computer languages, stores floats in binary. Â The values 1.6 and 0.6 aren&#39;t exactly representable in the internal format used, so the stored versions of 1.6 and 0.6 are actually just very close approximations to those values. Â It just so happens that the approximation for 1.6 is a tiny amount larger than 1.6 (the exact value stored is 1.600000000000000088817841970012523233890533447265625), while the approximation for 0.6 is a tiny amount smaller than 0.6 (the exact value is 0.59999999999999997779553950749686919152736663818359375).<br>

<br>
I recommend looking at the appendix to the Python tutorial for more information about floating point:<br>
<br>
<a href="http://docs.python.org/tutorial/floatingpoint.html" target="_blank">http://docs.python.org/tutorial/floatingpoint.html</a><br>
<br>
----------<br>
nosy: +mark.dickinson<br>
resolution: Â -&gt; invalid<br>
status: open -&gt; closed<br>
<div><div></div><div class="h5"><br>
_______________________________________<br>
Python tracker &lt;<a href="mailto:report at bugs.python.org">report at bugs.python.org</a>&gt;<br>
&lt;<a href="http://bugs.python.org/issue7704" target="_blank">http://bugs.python.org/issue7704</a>&gt;<br>
_______________________________________<br>
</div></div></blockquote></div><br><br clear="all"><br>-- <br>Pedro Flores C.<br>Estudiante Memorista de Informática 2009-2010<br>Universidad de Concepción, Concepción<br>Chile<br>