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MathGroup Archive 2004

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Re: Named Patterns in Switch

  • To: mathgroup at
  • Subject: [mg48948] Re: Named Patterns in Switch
  • From: Jens-Peer Kuska <kuska at>
  • Date: Fri, 25 Jun 2004 02:58:12 -0400 (EDT)
  • Organization: Universitaet Leipzig
  • References: <cbe8ta$svc$>
  • Reply-to: kuska at
  • Sender: owner-wri-mathgroup at


foo[expr_] := expr /. {(a_.)*x^(n_) :> a, (a_.)*y^(n_) :> n}



David Park wrote:
> Dear MathGroup,
> Here is an attempted routine using Switch that does not work.
> foo[expr_] :=
>  Switch[expr,
>         (a_.)*x^(n_), a,
>         (a_.)*y^(n_), n]
> foo[3*x^3]
> a                       (I was hoping for 3)
> Switch uses patterns, but any named patterns are useless. So the a in the third argument in Switch has nothing to do with the a_. in the second argument.
> Is there some Mathematica construction that will test successive patterns with names, do a calculation with the first match and use the names in the patterns?
> David Park
> djmp at

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