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MathGroup Archive 2007

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Re: removing those annoying $$$$'s from local variables names?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg79716] Re: removing those annoying $$$$'s from local variables names?
  • From: David Bailey <dave at Remove_Thisdbailey.co.uk>
  • Date: Thu, 2 Aug 2007 03:57:03 -0400 (EDT)
  • References: <f8pk78$2i1$1@smc.vnet.net>

Nasser Abbasi wrote:
> Hello;
> 
> This is a problem I am sure many have seen. May be there is a simple
> solution for it, but I can't find it.
> 
> This problem is when a function returns back a symbol which is local
> to the function, then these synbols will have $nnnn tacked to them,
> and so when the caller say prints the symbol, it will have those $'s
> numbers, which make it annoying to look it and print, say as a table
> or such.
> 
> This is an example:
> 
> ------------- example 1 -------------
> 
> foo[] := Module[{c, k},
>               c = Array[k, 3]
>           ];
> 
> c = foo[];
> Print[c];
> 
> {k$76[1], k$76[2], k$76[3]}
> --------------------------------------------------
> 
> You see, since k is local to foo[], then when I print it, I see those $
> $$ signs.
> 
> Only way to remove this $$$'s is to make k global as follows
> 
> ------------------------ example 2 -------------------
> Remove[k];
> foo[] := Module[{c},
>               c = Array[k, 3]
>           ];
> 
> c = foo[];
> Print[c];
> 
> {k[1], k[2], k[3]}
> ----------------------------------------
> 
> But making 'k' global is something I do NOT want to do, since now I
> have to worry about 'k' having a value somewhere else in the code, and
> it goes against the whole idea of encapsulation. If I start making all
> my symbols global, then the code becomes hard to manage.
> 
> So, what should one do in this case?  How can make all the symbols
> local to a function, but at the same time not see these $$$'s when the
> symbols are used when they are returned from the function back to the
> caller?
> 
> thanks,
> Nasser
> 
> 
The point is that symbols local to a Module should not ideally be 
returned - most people consider this to be a mistake. Every symbol must 
have a name, and to a first approximation the only difference between a 
local name and a global one is the $... appended to the name.

Why not tell us a bit more about what you are trying to do.

David Bailey
http://www.dbaileyconsultancy.co.uk


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