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Re: On default numerical precision

  • To: mathgroup at smc.vnet.net
  • Subject: [mg90705] Re: On default numerical precision
  • From: sergio_r at mail.com
  • Date: Sun, 20 Jul 2008 06:33:22 -0400 (EDT)
  • References: <g5pj07$qbc$1@smc.vnet.net> <g5s9q0$51h$1@smc.vnet.net>

Jens thanks for you reply. I am not sure what
I am missing but here are the results of following
the sugested approach:

In[1]:= $Post = ( # /. a_Real :> NumberForm[a, {32, 16}]) &;

In[2]:= a=2.

Out[2]//NumberForm= 2.

In[3]:= b=3.

Out[3]//NumberForm= 3.

In[4]:= a*b

Out[4]//NumberForm= 6.

But the following form works the way I was looking
for:

In[5]:= $Post =.

In[6]:= $Post

Out[6]= $Post

In[7]:= $Post = ( # /. a_Real :> SetPrecision[a, 32]) &;

In[8]:= a=2.

Out[8]= 2.0000000000000000000000000000000

In[9]:=  b=3.

Out[9]= 3.0000000000000000000000000000000

In[10]:= a*b

Out[10]= 6.0000000000000000000000000000000

Thanks again,

Sergio


On Jul 19, 4:49 am, Jens-Peer Kuska <ku... at informatik.uni-leipzig.de>
wrote:
> Hi,
>
> $Post = ( # /. a_Real :> NumberForm[a, {32, 16}]) &;
>
> Regards
>    Jens
>
> sergi... at mail.com wrote:
> > Hello all,
>
> > I am wonderin on how to change the mathematica default printing
> > precision, so I don't have to type on any defined constant the
> > required  precision, like " `30 "  in:
>
> > In[1]:= a=2.3`30; b=2.1`30;
>
> > In[2]:= a*b
>
> > Out[2]= 4.83000000000000000000000000000
>
> > I would like  to be able to do:
>
> > a=2.3; b=2.1; and obtain
> > a*b = 4.83000000000000000000000000000
>
> > Regards,
>
> > Sergio
> > PS. Apparently the internal variable $Pre could be set to do that, but
> > the respective help page [  http://reference.wolfram.com/mathematica/ref/$Pre.html
> >    ] is not clear about how to do that.



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