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MathGroup Archive 2002

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Re: Subscript[x, y] and the Symbol x

  • To: mathgroup at smc.vnet.net
  • Subject: [mg33804] Re: Subscript[x, y] and the Symbol x
  • From: Hartmut Wolf <hartmut.wolf at t-systems.com>
  • Date: Tue, 16 Apr 2002 03:52:05 -0400 (EDT)
  • Organization: T-Systems GEI
  • References: <a93b61$pi2$1@debis.com>
  • Sender: owner-wri-mathgroup at wolfram.com

Curt Fischer schrieb:
> 
> Dear Mathgroup:
> 
> The Subscript function in Mathematica has no built-in meaning.  What
> definition can I give this function to allow me to use Subscript[x,y] as
> a "stand-alone" symbol that is completely distinct from the Symbol x or
> the Symbol y?  For example:
> 
> In[1]:=
> \!\(f[x_, y_] := x\_y\  + \ x + y\)
> 
> In[2]:=
> f[2,2]//FullForm
> 
> Out[2]//FullForm=
> Plus[4,Subscript[2,2]]
> 
> This is exactly what I don't want.  Instead I want
> Plus[4,Subscript[x,y]].  Is there a way to do this?
> 
> Thanks for your help.
> --
> Curt Fischer
> Tokyo Institute of Technology
> Dept. of Bioengineering

Curt,

to treat subscripted expressions as symbols best use the function Symbolize from
the notation package:

In[5]:= << Utilities`Notation`

assuming your function is something like

In[9]:= f[s_Symbol, x_, y_] := s + x + y

then first symbolize your subscripted expression by first entering

Symbolize[\[Placeholder]]

from -- and that is important! -- the Notation Palette. At placeholder enter x
then ctrl+shift+_ then y then ctrl+space and evaluate. You get something like
this

In[12]:=
\!\(\*
  RowBox[{"Symbolize", "[", 
    TagBox[\(x\_y\),
      NotationBoxTag,
      TagStyle->"NotationTemplateStyle"], "]"}]\)


What is important is the NotationBoxTag. If you just enter

In[11]:=
\!\(Symbolize[x\_y]\)

things wouldn't work. After this prelude, you can use x\_y as a symbol wherever
you like:

In[13]:=
\!\(f[x\_\(\(y\)\(\ \)\), 2, 3]\)
Out[13]=
\!\(5 + x\_y\)

Of course there is no point in this function f, you may simply enter

In[15]:=
\!\(x\_y + 2 + 3\)
Out[15]=
\!\(5 + x\_y\)

or, if you like

In[16]:=
\!\(x\_y = 2 + 3\)
Out[16]=
5

In[17]:=
\!\(x\_y\)
Out[17]=
5

--
Hartmut Wolf



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