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MathGroup Archive 2002

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Re: Generate expression from result

  • To: mathgroup at smc.vnet.net
  • Subject: [mg32829] Re: Generate expression from result
  • From: Albert Retey <albert.retey at visualanalysis.com>
  • Date: Thu, 14 Feb 2002 01:43:57 -0500 (EST)
  • Organization: Visual Analysis AG
  • References: <a4aum0$bug$1@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Johannes Ludsteck wrote:
> 
> Dear Mathgroup Members,
> I obtain the vector {x1,x2} as solution to a
> (rather complicated) equation system
> 
> {x1,x2}=LinearSolve[m[{a1,a2}],b[{a1,a2}]]
> Of course, the xi are functions of {a1,a2}.
> 
> Since I use the xi later on for complex operations,
> it would be of gread help if the arguments ai appeared
> in the vector {x1,x2}.
> Therefore I defined
> f[{a1_,a2_}]=LinearSolve[m[{a1,a2}],b[{a1,a2}]]
> 
> (I need "=" here instead of ":=", since f[] is called
> often and the LinearSolve[] command uses some time,
> since the vectors {x1,x2} and {a1,a2} are only
> examples and can have dimension 10 to 20 in my application.
> 
> Up to now the solution works well, but I am bothering
> whether this construction could generate modularity or
> naming problems, since the Assignment
> appears in a Module where {a1,a2} are defined as local variables.
> 
> fun[...]:=Module[{a1,a2,f},
>         ...
>         f[{a1_,a2_}]=LinearSolve[m[{a1,a2}],b[{a1,a2}]]
>         ...
> ]
> 
I think they are save, as you can see when evaluating the following.

Module[{a1, a2, f}, f[{a1_, a2_}] = LinearSolve[m[{a1, a2}], b[{a1,
a2}]];
  Print[DownValues[f]];
  Print[a1];
  Print[a2];
  ]

If things get more complicated I don't know, but why not just use
different names for the f-pattern to be on the save side?

HTH 

Albert


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