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what would cause a symbol not to clear using Clear[name] or Remove[name]?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg127211] what would cause a symbol not to clear using Clear[name] or Remove[name]?
  • From: "Nasser M. Abbasi" <nma at 12000.org>
  • Date: Sun, 8 Jul 2012 19:05:48 -0400 (EDT)
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  • Reply-to: nma at 12000.org

Any experts here would explain why such a strange thing can happen?

I do Clear[y] and then do ??y and it still shows the same expression as before.

I also tried Remove[y], and it is still not clearing.

--------------------------
In[132]:= Clear[y]

In[133]:= y
Out[133]= 1/208694150 (0. -3.53899*10^6 x+63800. x^3+12500/3 (-7.5+x)^4 UnitStep[-7.5+x]-12500/3 (-0.9+x)^4 UnitStep[-0.9+x])

In[134]:= Remove[y]
In[135]:= y
Out[135]= 1/208694150 (0. -3.53899*10^6 x+63800. x^3+12500/3 (-7.5+x)^4 UnitStep[-7.5+x]-12500/3 (-0.9+x)^4 UnitStep[-0.9+x])

In[136]:= ??y
Global`y
y=(0. -3.53899*10^6 x+63800. x^3+12500/3 (-7.5+x)^4 UnitStep[-7.5+x]-12500/3 (-0.9+x)^4 UnitStep[-0.9+x])/208694150

In[140]:= Clear["Global`*"]
In[141]:= y
Out[141]= beamDeflection[10,0.09,0.25,0.5,100000,0,29000000000,143927/20000000,1,x]

In[142]:= Remove["Global`*"]
In[143]:= y
Out[143]= beamDeflection[10,0.09,0.25,0.5,100000,0,29000000000,143927/20000000,1,x]
--------------------------------

?Remove
removes symbols completely, so that their names are no longer recognized by Mathematica.

In[139]:= $Version[]
Out[139]= 8.0 for Microsoft Windows (64-bit) (October 6, 2011)[]

Here is a video of it in this folder, but it is 70 MB AVI file (in need
to figure out how to reduce the size of an AVI file). This in
case someone thinks I am making this up :)

http://12000.org/tmp/070812/

Only after I close the kernel, will this symbol finally clear up.

In[2]:= y
Out[2]= y

Do you think this is strange? or is there a rational explanation to it?
I have thought always that Clear[] will clear a symbol.

thanks,
--Nasser










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