Re: Beware of adding 0.0
- To: mathgroup at smc.vnet.net
- Subject: [mg50212] Re: [mg50206] Beware of adding 0.0
- From: stephen layland <layland at wolfram.com>
- Date: Sat, 21 Aug 2004 03:04:13 -0400 (EDT)
- References: <200408200858.EAA12526@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
so spake paul [2004.08.20 @ 04:48]:
> In Mathematica 5.0, I get a very strange result when I add 0.0 to a number,
> why is this? See below:
>
> p = SetPrecision[314159265358979323, 25]
> q = SetPrecision[314159265358979323., 25]
> r = SetPrecision[314159265358979323.00000000000000000000, 25]
> s = SetPrecision[p + 0.0, 25]
0.0 has $MachinePrecision. You can't expect p (with precision 25) + 0.0
(precision 15.9...) to have automatically have 25 digits of precision...
In[5]:= Precision/@{p, 0.0}
Out[5]= {25., MachinePrecision}
In[6]:= Precision[p+0.0]
Out[6]= MachinePrecision
The correct method should be:
In[7]:= t = p + SetPrecision[0.0, 25];
Precision[t]
Out[8]= 25.
-ste\/e
--
/*-----------------------------*\
| stephen layland |
| Technical Support Engineer |
| layland at wolfram.com |
\*-----------------------------*/
- References:
- Beware of adding 0.0
- From: "paul" <paul_tan@aoI.com>
- Beware of adding 0.0