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Re: Positions of Polynomials in expr?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg109354] Re: Positions of Polynomials in expr?
  • From: DrMajorBob <btreat1 at austin.rr.com>
  • Date: Fri, 23 Apr 2010 03:48:07 -0400 (EDT)

A pattern can BE a condition. For instance, x_?Negative or x_?(#<0&) or  
x_/;0<x<1

Bobby

On Thu, 22 Apr 2010 02:29:38 -0500, Jack L Goldberg 1 <jackgold at umich.edu>  
wrote:

> Hi Folks,
>
> "Select" and "Cases" are commands that do essentially the same thing,
> namely, pick out elements of a list which, in the first case matches a
> criterion, in the second case, matches a pattern.  I call these
> parallel commands.  Is there a command parallel to "Position" which
> uses criterion rather than pattern matching?
>
> If no such parallel function exists, can one easily construct one?
>
> I actually have a special case in mind.  I want to find the position
> of all parts of expr which fail the test PolynomialQ[f_,x].  Naively,
> I thought one might Map
> Polynomial[#,x]& to all levels of expr and then find the positions of  
> "False".
> I haven't tried it because I'm betting someone knows how to do this
> neatly and I do not like to re-invent the wheel.  When I do so, the
> wheel tends to be more like an oval than a circle.
>
> Thanks!
>
> Jack
>


-- 
DrMajorBob at yahoo.com


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