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MathGroup Archive 2001

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Re: FractionalPart

  • To: mathgroup at
  • Subject: [mg31255] Re: [mg31232] FractionalPart
  • From: Tomas Garza <tgarza01 at>
  • Date: Tue, 23 Oct 2001 04:53:34 -0400 (EDT)
  • References: <>
  • Sender: owner-wri-mathgroup at

The situation you describe has to do with the way Mathematica handles
numbers. Integers are exact, while reals are approximate. When you use
Log[a], where a is a list of integers, the whole expression becomes real,
and a very small error is introduced, in apparent contradiction to the
obvious. In your example below,




The Help browser says "For exact numeric quantities, FractionalPart
internally uses numerical approximations to establish its result. This
process can be affected by the setting of the global variable
$MaxExtraPrecision. "

Tomas Garza
Mexico City
----- Original Message -----
From: "Juan" <erfa11 at>
To: mathgroup at
Subject: [mg31255] [mg31232] FractionalPart

> Hello.
> I am new in Mathematica(also in english), and I have this question:
> I would like to know the behavior of the function FractionalPart.
> See here:
> In[1]:= a=Range[9]^2
> Out[1]= {1,4,9,16,25,36,49,64,81}
> In[2]:= x=Exp[.5 Log[a]]
> Out[2]= {1,2.,3.,4.,5.,6.,7.,8.,9.}
> In[3]:= FractionalPart[x]
> Out[3]= {0,0.,4.444089x10^-16,0.,0.,1.,0.,0.,1.,1.77639x10^-15}
> But it shoud be 0., all of them,no?
> Thanks. Juan
> _________________________________________________________________
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