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MathGroup Archive 2006

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Re: MemberQ

  • To: mathgroup at smc.vnet.net
  • Subject: [mg68521] Re: [mg68503] MemberQ
  • From: "Adriano Pascoletti" <pascolet at dimi.uniud.it>
  • Date: Wed, 9 Aug 2006 04:18:14 -0400 (EDT)
  • Sender: owner-wri-mathgroup at wolfram.com

Bruce Colletti wrote ..
> Re Mathematica 5.2.0.0.
> 
> Since 0.7 is in the set {0.0, 0.1, 0.2,..., 0.9, 1.0}, why does MemberQ[Range[0.,
> 1., .1], .7] return False?
>  
> Thankx.
> 
> Bruce
> 

Because the 0.7 in Range[0.0, 1.0, 0.1] is

In[11]:=
Range[0.0,1.0,0.1][[8]]//FullForm
Out[11]//FullForm=
0.7000000000000001`

and

In[9]:=
FullForm[0.7]
Out[9]//FullForm=
0.7`

They differ on the 16th decimal place as can be seen  evaluating 
0.7 - Range[0.0, 1.0, 0.1]



Adriano Pascoletti


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