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Module Behavior

• To: mathgroup at smc.vnet.net
• Subject: [mg84660] Module Behavior
• From: "Marcelo Mayall" <mmayall at bol.com.br>
• Date: Tue, 8 Jan 2008 03:37:46 -0500 (EST)

One of the main features of the function Module is that you can specify 
symbols to be treated as local. For example:

In[1]:=   Module[{a, b}, a = b; b = 1;]
In[2]:=   {Names["a$*"], Names["b$*"]}

Out[2]= {{}, {}}

However, if we change the local symbol "b" to "b[1]" it does not treat 
as local anymore.

In[3]:=  Module[{a, b}, a = b[1]; b[1] = 1;]
In[4]:=  {Names["a$*"], Names["b$*"]}

Out[4]= {{}, {"b$69"}}

And each time you execute this command line a new variable "b$*" will be 
created. 

In[14]:= Module[{a, b}, a = b[1]; b[1] = 1;]
In[15]:= {Names["a$*"], Names["b$*"]}

Out[15]= {{}, {"b$69", "b$77", "b$79", "b$81", "b$84", "b$86", "b$88", 
"b$90", "b$92", "b$94"}}


Shouldn't the function Module treat the symbol "b[1]" as local too?
Is this an expected or unexpected result?

Regards,
Marcelo Mayall

• Follow-Ups:
  • Re: Module Behavior
    • From: Carl Woll <carlw@wolfram.com>