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Re: Can't Remove[] variable "K"? (Really strange behavior . . . )

• To: mathgroup at smc.vnet.net
• Subject: [mg69143] Re: [mg69131] Can't Remove[] variable "K"? (Really strange behavior . . . )
• From: "Carl K. Woll" <carlw at wolfram.com>
• Date: Thu, 31 Aug 2006 04:38:52 -0400 (EDT)
• References: <200608301035.GAA28076@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

AES wrote:
> For years I've started every notebook with the input line
> 
>    x; Remove["Global`*"];
> 
> so every calculation will start more or less "fresh".  Recently a 
> calculation exhibited weird behavior involving a variable "K", which 
> didn't seem to get removed or cleared by Remove[].   I eventually boiled 
> this down to a simple free-standing 5 Input cell notebook as follows:  
> 
>    x; Remove["Global`*"];
>    K=0.6;
>    Remove["Global`*"];
>          Remove::"rmnsm" 
>          There are no  symbols matching "Global`*".   More�
>    K
>          0.6
>    ??K
>          K is a default generic name for a summation index in a symbolic 
>          sum.
>          K = 0.6
> 

Notice the usage message for K. This is because K is a System symbol:

In[2]:= Context[K]

Out[2]= System`

Carl Woll
Wolfram Research

> Notes:
> 
> 1)  This is on a Mac iBook G4, OS 10.3.9, Mathematica 5.1.0.0.
> 
> 2)  Each single-indent line is an Input cell; double-indent lines are 
> Output cells.  Behavior repeats the same after re-typing all the cells 
> into a fresh notebook; after quitting and re-starting Mathematica; after 
> shutting down and restarting the Mac.
> 
> 3)  I appreciate that user variables preferably start with lower case -- 
> but other single-cap-letter symbol names work OK, and doing Help on "K" 
> brings up nothing special associated with K by itself.
> 
> [And by the way, how can one select a sequence of cells in a notebook 
> and copy all their contents -- including error msgs -- to paste in as 
> above, without having to retype most of the stuff?)

• References:
  • Can't Remove[] variable "K"? (Really strange behavior . . . )
    • From: AES <siegman@stanford.edu>