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MathGroup Archive 2004

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Re: Unexpected Result for InputForm

  • To: mathgroup at smc.vnet.net
  • Subject: [mg47600] Re: Unexpected Result for InputForm
  • From: drbob at bigfoot.com (Bobby R. Treat)
  • Date: Sat, 17 Apr 2004 02:31:40 -0400 (EDT)
  • References: <c5oasf$1fd$1@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Observe:

x = 1.23456789012345678901234\
56789`29.091514977212704*^9; 
doubt = 10^(-20); 
Log[10, doubt/x]
-29.0915149772126998957108302\
78233886544289266752931`30.61\
646700851524

InputForm[x + doubt]
1.234567890123456789012345678\
91`29.091514977212704*^9

InputForm[x - doubt]
1.234567890123456789012345678\
89`29.091514977212704*^9

"Doubt" is one digit in the last place (10^-20), so relative doubt is
that divided by x. Precision is the log base 10 of relative doubt.

Bobby

Harold.Noffke at wpafb.af.mil (Harold Noffke) wrote in message news:<c5oasf$1fd$1 at smc.vnet.net>...
> $Version "5.0 for Microsoft Windows [2000] (November 18, 2003)"
> 
> MathGroup:
> 
> In[5]:=
> 	$NumberMarks
> Out[5]=
> 	Automatic
> In[6]:=
> 	x=1234567890.12345678901234567890;
> In[7]:=
> 	InputForm[x]
> Out[7]//InputForm=
> 	1.2345678901234567890123456789`29.091514977212704*^9	
>                                                                     
> In Out[7], the `29 says there are 29 digits (correct); the *^9 says
> x10**9 (correct); but the .091514977212704 in between I can't figure
> out.  What does this string of numbers mean, and where is it's
> documentation?
> 
> Thanks.
> Harold


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