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MathGroup Archive 2005

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Re: local symbols inside Module

  • To: mathgroup at smc.vnet.net
  • Subject: [mg55987] Re: local symbols inside Module
  • From: Peter Pein <petsie at arcor.de>
  • Date: Wed, 13 Apr 2005 01:10:11 -0400 (EDT)
  • References: <d3g81p$s8r$1@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

OT wrote:
> Hi all, I have some problems in working with local variables inside 
> Module: I wrote this function:
> 
> RealLinearCombination[v_List]:=Module[{d,coeffs},
> d=Legth[v];
> 
> coeff=Table[ToExpression["c"<>ToString[k]],{k,d}];
> 
> coeffs=coeffs/.Solve[eqns,coeffs];
> 
> ....
> ....
> 
> ]
> 
> The function works, but has a big limitation: the elements of the list 
> coeffs are not local symbols!
> 
> Since the elements of the list coeffs are not local variables, if I run 
> my function when I have already initialized a symbol like c3=Pi, say, I 
> get an error because mathematica tries to execute 
> Solve[eqns,{c1,c2,Pi,c4,...,cd}] since c3 has been already initialized 
> as a number.
> 
> So, my question is: how can I initialize a local list of symbols
> {c1,...cd} inside a Module, when d is an argument supplied to the Module 
> itself?
> 
> Thanks for every answer!
> 
If your equations (eqns) are built inside the module using coeffs, you
can (should) use coeffs=Table[Unique[c],{d}]. Instead of e.g.
eq1=c1*x+c2 you'll have to use eq1=coeffs[1]*x+coeffs[2].

-- 
Peter Pein
Berlin


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