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MathGroup Archive 1999

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Question on symbols in modules

  • To: mathgroup at smc.vnet.net
  • Subject: [mg17945] Question on symbols in modules
  • From: "David Keith" <dkeith at hevanet.com>
  • Date: Sat, 5 Jun 1999 02:56:10 -0400
  • Organization: Hevanet Communications
  • Sender: owner-wri-mathgroup at wolfram.com

Perhaps I am confused about symbols in modules, and also about evaluation. I
execute the lines below in V4.0 on NT4.0/SP3:

In[1]:= Names["Global`*"]
Out[1]= {}

In[2]:= test[] := Module[{tmp}, Return[tmp]]

In[3]:= Names["Global`*"]
Out[3]= {"test", "tmp"}

In[4]:= test[]
Out[4]= tmp$5

What confuses me is this: line In[2] defines a module with local symbol
"tmp". But following this line, a symbol "tmp" has been created in Global
context. I thought this would not happen, that the only symbol ever created
would be a temporary symbol, some "tmp$N". Further, I thought that the right
hand side of In[2] would not actually be evaluated until called.

In[4] / Out[4] does display the behaviour I expected, a temporary symbol is
used within the scope of the module, but why is "tmp" ever created?

Thanks.





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