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

*To*: mathgroup at smc.vnet.net*Subject*: [mg58496] Re: [mg58426] how to find n in expression x^n using a pattern?*From*: stephen layland <layland at wolfram.com>*Date*: Mon, 4 Jul 2005 02:24:28 -0400 (EDT)*Mail-followup-to*: steve <nma124@hotmail.com>, mathgroup@smc.vnet.net*References*: <200507020806.EAA01589@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

and thus spake steve [2005.07.02 @ 04:08]: > 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 Here' ssomething that might work for you: (Exponent[Cases[p, x | x^n_], x] /. {} -> {0})[[1]] It's kind of ugly, but like someone suggested before, first we use cases to find any occurance of x or x^n_ by itself in the multiplication expression. We then use the function Exponent to turn the x^n_ or x into n or 1. Lastly, we explicitly set the exponent to 0 if we didn't find anything, and get rid of the list enclosure. I'm sure there are other methods, however. Happy hacking! -- /*------------------------------*\ | stephen layland | | Documentation Programmer | | http://members.wri.com/layland | \*------------------------------*/

**References**:**how to find n in expression x^n using a pattern?***From:*"steve" <nma124@hotmail.com>