how to find n in expression x^n using a pattern?

*To*: mathgroup at smc.vnet.net*Subject*: [mg58426] how to find n in expression x^n using a pattern?*From*: "steve" <nma124 at hotmail.com>*Date*: Sat, 2 Jul 2005 04:06:25 -0400 (EDT)*Sender*: owner-wri-mathgroup at wolfram.com

I am learning patterns in Mathemtica, and I thought this will be easy. suppose you are given a factored expression, such as x^n(x^2+2)(x^3+4) where 'n' above can be any number, including zero (i.e. there is no (x) as a separate factor). I need to find 'n', which can be 0,1,2,3,..etc.. i.e I need to find the power of the factor x by itself if it exist in the expression. not (x^n+anything), just (x^n) byitself. For example p= x (x^2+2) ---> here n=1 I tried this p /. x^n_(any_) -> n This did not work since x^1 does not match pattern x^n_. I would have worked if I had x^2 (x^3+2) for example. I know that I need to use something like x^_:1 to make it match x, which is really x^1, but I do not know how to use it in a replacement rule, becuase when I write p /. (x^n_:1)(any_) -> n it is an error. If I write p /. (x^_:1)(any_) -> _ I do not get back anything. Next I tried the Cases command, and again had no luck. The main problem is that Mathematica makes a difference between x, x^1, and x^2, etc... when it comes to matching with pattern x^n_ any idea how to do this? thanks, steve

**Follow-Ups**:**Re: how to find n in expression x^n using a pattern?***From:*Pratik Desai <pdesai1@umbc.edu>

**Re: how to find n in expression x^n using a pattern?***From:*stephen layland <layland@wolfram.com>

**Re: how to find n in expression x^n using a pattern?***From:*Andrzej Kozlowski <akozlowski@gmail.com>