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Re: Alternative to defining 'operator' function?

  • To: mathgroup at
  • Subject: [mg47637] Re: Alternative to defining 'operator' function?
  • From: Paul Abbott <paul at>
  • Date: Mon, 19 Apr 2004 04:33:07 -0400 (EDT)
  • Organization: The University of Western Australia
  • References: <c5o9o1$181$>
  • Sender: owner-wri-mathgroup at

In article <c5o9o1$181$1 at>,
 "Owen, HL (Hywel)" <H.L.Owen at> wrote:

> Paul's idea is a good one if you need to generate a symbolic set of
> expressions (not right for my problem though):
> Subscript[R, n_][v_] := Subscript[R, n]
> Rest[ComposeList[Subscript[R,1], Subscript[R,2], Subscript[R,3]}, v]]

This code works fine in general. For example, suppose your set of 
matrices is

 Subscript[A, n_] := {{a[n],b[n]},{c[n],d[n]}}

and the vector is 

 v = {x,y}

If you modify the definition of Subscript[R, n_][v_] to

 Subscript[R, n_][v_] := Subscript[A, n] . v


  Rest[ComposeList[{Subscript[R,1], Subscript[R,2], Subscript[R,3]}, v]]

does what you want.


Paul Abbott                                   Phone: +61 8 9380 2734
School of Physics, M013                         Fax: +61 8 9380 1014
The University of Western Australia      (CRICOS Provider No 00126G)         
35 Stirling Highway
Crawley WA 6009                      mailto:paul at 

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