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MathGroup Archive 1996

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Re: can an "array" start with an index other than 1?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg4728] Re: can an "array" start with an index other than 1?
  • From: wagner at motel6.cs.colorado.edu (Dave Wagner)
  • Date: Sat, 31 Aug 1996 03:57:45 -0400
  • Organization: University of Colorado, Boulder
  • Sender: owner-wri-mathgroup at wolfram.com

In article <4vqihp$qrn at dragonfly.wolfram.com>,
Steve Sutlief <steve at gandalf.radonc.washington.edu> wrote:
>I would like to have a multidimensional array with an index running 
>from -5 to 5, for example.  Is there a kludge for doing this in 
>Mathematica?
>
>The two kludges I could use in C won't work in Mathematica:
>
>#define b(x) a[x+5]

No?  Why not define

	b[x_] := a[[x+6]]

and use b[-5] to refer to a[[1]], analogous to what you did in your
C program?

In fact, Mathematica can even make it look like b is being indexed,
not called as a function (try getting this to work in C!), by doing this:

	b /: b[[x_]] := a[[x+6]]

Now you can use b[[-5]], rather than b[-5], to refer to a[[1]].
But the first way might even be prefereable to you, since it looks
more like C and you're obviously a C programmer at heart.

		Dave Wagner
		Principia Consulting
		(303) 786-8371
		dbwagner at princon.com
		http://www.princon.com/princon

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