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Re: String-to-Number Conversion Precision

• To: mathgroup at smc.vnet.net
• Subject: [mg112355] Re: String-to-Number Conversion Precision
• From: Albert Retey <awnl at gmx-topmail.de>
• Date: Fri, 10 Sep 2010 05:11:05 -0400 (EDT)
• References: <i6crfo$sa1$1@smc.vnet.net>

Am 10.09.2010 10:50, schrieb Ben:
> I'm reading real numbers from a file and I'm trying to convert them
> from string format (with arbitrary precision) to real values with the
> same precision as given in the strings.
> 
> For example, when I convert "1.867524468", I want the result to be set
> to precision 10.  Instead, I get the following.
> 
> In[1]:=    string = "1.867524468"
> Out[1]:= "1.867524468"
> 
> In[2]:=    x = ToExpression[string]
> Out[2]:= 1.86752
> 
> The last 4-digits get cut off.  This is fine for when I do math with
> the number because the extra digits are still stored, but not when I
> want to rewrite the number to a different file.  When I convert the
> number back to a string for file output, the last 4-digits remain
> lost.
> 
> In[3]:=    ToString[x]
> Out[3]:= "1.86752"
> 
> Is there a function or formula I can use to automatically set the
> precision of these numbers to their precision in the string?  Thanks.
> 
ToString[NumberForm[x, 10]]

hth,

albert