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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


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