Re: Replace, test question

*To*: mathgroup at smc.vnet.net*Subject*: [mg120327] Re: Replace, test question*From*: Bob Hanlon <hanlonr at cox.net>*Date*: Tue, 19 Jul 2011 06:55:43 -0400 (EDT)*Reply-to*: hanlonr at cox.net

data /. _?PrimeQ -> P data /. x_ /; PrimeQ[x] -> P Bob Hanlon ---- PA32R <tio540s1 at gmail.com> wrote: ============= I'm very new to Mathematica and trying to work my way through it. I don't understand why: {58, 61, 15, 66, 10, 2, 24, 81, 45, 84} /. x_ /; PrimeQ -> P returns: {58, 61, 15, 66, 10, 2, 24, 81, 45, 84} I would expect it to take the list, replace everything in the list that matches any pattern and passes the PrimeQ test, i.e., is prime, with P to yield: {58, P, 15, 66, 10, P, 14, 81, 45, 84} Can someone explain my misunderstanding? Thanks. -- Bob Hanlon