Select peculiarity
- To: mathgroup at smc.vnet.net
- Subject: [mg16384] Select peculiarity
- From: Jack Goldberg <jackgold at math.lsa.umich.edu>
- Date: Thu, 11 Mar 1999 02:16:52 -0500
- Sender: owner-wri-mathgroup at wolfram.com
Hi Group, I have an expression f[x] from which I want to pick out polynomials in x. Consider this method: test[f_,x_] := Select[ f, PolynomialQ[#,x]& ] Now f need not be a list as the following examples show. Ex 1. test[x^2+2x -1 + g[x],x] returns x^2+2x+1 Ex2. test[(x^2+x-1)*g[x],x] returns x^2+2x+1 Exactly what I expected. One more successful example. Ex3. test[(x+1)(x-1)g[x],x] returns (x+1)(x-1) Here is the puzzle. Ex4. test[g[x]*h[x],x] returns 1 Anyone know what's going on? I am using Version 3.0 on both a Sun unix machine and a PowerMac. Jack