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MathGroup Archive 2004

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Re: Information about subscripted function

  • To: mathgroup at smc.vnet.net
  • Subject: [mg53077] Re: Information about subscripted function
  • From: Paul Abbott <paul at physics.uwa.edu.au>
  • Date: Wed, 22 Dec 2004 04:53:23 -0500 (EST)
  • Organization: The University of Western Australia
  • References: <cq8tj5$h18$1@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

In article <cq8tj5$h18$1 at smc.vnet.net>, seb at magda.ifj.edu.pl wrote:

> when I define a function with a subscript in its
> name: (cell content below)
> 
> In[1]:= \!\(f\_1[x_] := x^2\)
> 
> I can't see it by use of information operator:
> 
> In[2]:= \!\(\(?\ f\_1\)\)
> 
> Information::ssym
> 
> Out[2]:= \!\(Information[f\_1, LongForm -> False]\)
> 
> of course I may ask:
> 
> In[3]:= ? Subscript
> 
> but then I get ALL functions which have subscripts in their names!
> 
> so, how to ask about the defintions of subscripted functions ?

By default, the definition is associated with Subscript, not with f. In 
InputForm, your first input reads

  Subscript[f, 1][x_] := x^2

and so you can see why this is so. 

You could use Symbolize in the

  <<Utilities`Notation`

package to symbolize Subscript[f, 1] and then it will work.

Alternatively, you could use association. However, you cannot associate 
the definition with f using

  f /: Subscript[f, 1][x_] := x^2

However, you can achieve what you want using pure functions:

 f /: Subscript[f, 1] := Function[x, x^2]

 ?f

Cheers,
Paul

-- 
Paul Abbott                                   Phone: +61 8 6488 2734
School of Physics, M013                         Fax: +61 8 6488 1014
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Crawley WA 6009                      mailto:paul at physics.uwa.edu.au 
AUSTRALIA                            http://physics.uwa.edu.au/~paul


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