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

[pedro flores]

pedro flores <pflore...@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 <rep...@bugs.python.org>

>
> Mark Dickinson <dicki...@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 <rep...@bugs.python.org>
> <http://bugs.python.org/issue7704>
> _______________________________________
>

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

_______________________________________
Python tracker <rep...@bugs.python.org>
<http://bugs.python.org/issue7704>
_______________________________________
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:rep...@bugs.python.org";>rep...@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:dicki...@gmail.com";>dicki...@gmail.com</a>&gt; added the 
comment:<br>
<br>
This is not a bug:  Python, like many other computer languages, stores floats 
in binary.  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.  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:  -&gt; invalid<br>
status: open -&gt; closed<br>
<div><div></div><div class="h5"><br>
_______________________________________<br>
Python tracker &lt;<a 
href="mailto:rep...@bugs.python.org";>rep...@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>

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