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Re: Named Patterns in Switch


How's this?

foo[expr_]:=expr/.{(a_.)*x^(n_):>a,(a_.)*y^(n_):>n}
foo[3*x^3]

3

Bobby

On Thu, 24 Jun 2004 05:36:29 -0400 (EDT), David Park <djmp at earthlink.net> 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 earthlink.net
> http://home.earthlink.net/~djmp/
>
>
>
>



-- 
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