Re: Pattern matching

*To*: mathgroup at smc.vnet.net*Subject*: [mg116227] Re: Pattern matching*From*: DrMajorBob <btreat1 at austin.rr.com>*Date*: Mon, 7 Feb 2011 06:06:51 -0500 (EST)

fact[4] -> 4 fact[3] -> 4*3 fact[2] -> 12*2 fact[1] -> 24*1 fact[0] -> 24*0 fact[-1] == 0. Bobby On Sun, 06 Feb 2011 04:35:17 -0600, StatsMath <stats.math8 at gmail.com> wrote: > Have a question regarding the applicaiton of pattern rules: > > fact[4] //. {fact[n_] :> n fact[n-1], fact[0] -> 1} > > This is a bug since fact[0] needs to be defined 1st, but I expected > the above to grind away idefnitely but it returned a a value 0, > instead of an infininte computation. > > Can you help me understand why the above returns 0? > > Thanks! > -- DrMajorBob at yahoo.com