Mathematica 9 is now available
Services & Resources / Wolfram Forums
-----
 /
MathGroup Archive
2005
*January
*February
*March
*April
*May
*June
*July
*August
*September
*October
*November
*December
*Archive Index
*Ask about this page
*Print this page
*Give us feedback
*Sign up for the Wolfram Insider

MathGroup Archive 2005

[Date Index] [Thread Index] [Author Index]

Search the Archive

Re: Free variables in an expression

  • To: mathgroup at smc.vnet.net
  • Subject: [mg54860] Re: Free variables in an expression
  • From: Sascha Kratky <notvalid at notvalid.com>
  • Date: Fri, 4 Mar 2005 05:07:56 -0500 (EST)
  • References: <200503020626.BAA08074@smc.vnet.net> <d06160$krn$1@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Andrzej,

with "free" and "bound" I was actually referring to the meaning of
these terms  in  logic. So the solution you gave is exactly was I was
looking for.

Thanks,
Sascha

In article <d06160$krn$1 at smc.vnet.net>, Andrzej Kozlowski
<akoz at mimuw.edu.pl> wrote:

> The problem is that the OP completely failed to explain the meaning of  
> "free" and "bound". With the usual meaning of these terms in  logic the  
> following sentence:
> 
> expr=Exists[y, Element[y, Reals], x*y - 1 == 0]
> 
> contains just one free variable x.  In this case however
> 
> 
> Cases[expr, _Symbol?( !NumericQ[#1] & ), Infinity]
> 
> {y, y, Reals, y, x}
> 
> which is of course wrong. However,
> 
> 
> Union[Cases[Resolve[expr],_Symbol? 
> (FreeQ[Attributes[#],Protected]&),Infinity]]
> 
> {x}
> 
> returns the correct answer.
> 
> I have to admit I rather doubt that this is what the OP meant, but if  
> not than his use of "free" and "bound" is non-standard.
> 
> Andrzej Kozlowski
> 
> 
> On 2 Mar 2005, at 07:26, Bob Hanlon wrote:
> 
> > expr=Log[6x]+y/3-Exp[z]*Pi-3*I;
> >
> > Cases[expr, _Symbol?(!NumericQ[#]&),Infinity]
> >
> > {z,y,x}
> >
> >
> > Bob Hanlon
> >
> >>
> >> From: Sascha Kratky <notvalid at notvalid.com>
To: mathgroup at smc.vnet.net
> >> Date: 2005/03/01 Tue AM 01:58:13 EST
> >> Subject: [mg54860]  Free variables in an expression
> >>
> >> Is there a Mathematica built-in function that gives a list of free
> >> (unbound) variables in an arbitrary expression?
> >>
> >> Thanks,
> >> Sascha
> >>
> >>
> >
> >
>


  • Prev by Date: Re: Rearranging a data array containing calendrical as well as data entries.
  • Next by Date: Re: Re: Bug in Import?
  • Previous by thread: Re: Re: Free variables in an expression
  • Next by thread: Re: Free variables in an expression