Re: Alternative to defining 'operator' function?

• To: mathgroup at smc.vnet.net
• Subject: [mg47637] Re: Alternative to defining 'operator' function?
• From: Paul Abbott <paul at physics.uwa.edu.au>
• Date: Mon, 19 Apr 2004 04:33:07 -0400 (EDT)
• Organization: The University of Western Australia
• References: <c5o9o1\$181\$1@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

```In article <c5o9o1\$181\$1 at smc.vnet.net>,
"Owen, HL (Hywel)" <H.L.Owen at dl.ac.uk> 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

then

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

does what you want.

Cheers,
Paul

--
Paul Abbott                                   Phone: +61 8 9380 2734
School of Physics, M013                         Fax: +61 8 9380 1014
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AUSTRALIA                            http://physics.uwa.edu.au/~paul

```

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