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MathGroup Archive 1998

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Re: Up N' Down values.

  • To: mathgroup at
  • Subject: [mg13338] Re: [mg13240] Up N' Down values.
  • From: David Withoff <withoff>
  • Date: Mon, 20 Jul 1998 02:49:57 -0400
  • Sender: owner-wri-mathgroup at

> Hi there,
> I'm having some hard time trying to define "up values" to subscripted
> variables, what I would like to do is (Latex notations)
> d_1 /: Equal[d_1,0]:=False
> Ok, I know that the full form of d_1 is Subscript[d,1] so I've tried;
> Subscript /: Equal[Subscript[d,1],0]:=Flase
> and
> d /: Equal[Subscript[d,1],0]:=Flase
> but none seems to work, I get the error message:
> TagSetDelayed::"tagnf": "Tag d not found in False==0.
> which I don't understand.
> Any idea?
> Regards.
> \/\\/\/\/>> Gadi ORON <<\/\/\/\/
> EMAIL :  oron at
> Homepage : ICQ#7316619

I would need to see the rest of your input to know what the problem
might be.

The first input should work fine:

In[1]:= Subscript /: Equal[Subscript[d,1],0]:=False

In[2]:= Subscript[d,1]==0

Out[2]= False

The second input will fail because the symbol d occurs too deeply nested
in the left-hand side of the rule:

In[1]:= d /: Equal[Subscript[d,1],0]:=False

   Tag d in d  == 0 is too deep for an assigned rule to be found.

Out[1]= $Failed

That's not the message that you reported, however.  The message you
reported suggests that there must have been some other input.  If you
had, for example, loaded the Utilities`Notation` package, and used
Symbolize to cause the subscripted expression to be treated as a
symbol, that would explain the behavior that you reported, since these
assignments then amount to trying to attach rules to parts of a symbol,
like trying to attach a rule for f1 to f.

Dave Withoff
Wolfram Research

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