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Re: strange bug?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg79196] Re: [mg79126] strange bug?
  • From: Bob Hanlon <hanlonr at cox.net>
  • Date: Fri, 20 Jul 2007 03:38:55 -0400 (EDT)
  • Reply-to: hanlonr at cox.net

If you want exact results, use exact numbers.

For[n = 1, n < 20, n = n + 1/10, 
  Print[N[n], " ", IntegerPart[10*n]] 
  ] 

Although in this case the IntegerPart is unnecessary.

Bob Hanlon

---- Jeremy Price <cfgauss at u.washington.edu> wrote: 
> I think I've found a bug in mathematica 5.2,
> 
> In[418]:=
> $Version
> 
> Out[418]=
> 5.2 for Microsoft Windows (June 20, 2005)
> 
> When I run, eg, 
> 
> In[416]:= IntegerPart[10*5.1]
> 
> Out[416]= 51
> 
> I get what I expect.  But when I run the same thing in a loop, 
> 
> For[n = 1, n < 20, n = n + .1,
>   Print[n, " ", IntegerPart[10*n]]
>   ]
> 
> I get output like:
> 
> >From In[415]:= 4.2 42
> 
> >From In[415]:=4.3 43
> 
> >From In[415]:=4.4 44
> 
> >From In[415]:=4.5 45
> 
> >From In[415]:=4.6 46
> 
> >From In[415]:=4.7 47
> 
> >From In[415]:=4.8 48
> 
> >From In[415]:=4.9 48
> 
> >From In[415]:=5. 49
> 
> >From In[415]:=5.1 50
> 
> >From In[415]:=5.2 51
> 
> Any idea what's going on here or how to fix it?
> 



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