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