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Re: Bug 1+4/10

• To: mathgroup at smc.vnet.net
• Subject: [mg120067] Re: Bug 1+4/10
• From: Bill Rowe <readnews at sbcglobal.net>
• Date: Thu, 7 Jul 2011 07:32:44 -0400 (EDT)

On 7/6/11 at 5:40 AM, slawek at host.pl (slawek) wrote:

>Let check

>In[1]:= 1.4 == 1 + 4/10 Out[1]= True

>In[2]:= a = SetPrecision[1.4, 30] Out[2]=
>1.39999999999999991118215802999

>In[3]:= b = SetPrecision[1 + 4/10, 30] Out[3]=
>1.40000000000000000000000000000

>No comment is needed.

The question is why do you think this is a bug? In one case, you
are starting with a machine precsion number and increasing the
precision, something that really isn't wise. In the other case
you start with an exact value and reduce the precision. Why
would you expect the same result?