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Re: indeterminate expression

  • To: mathgroup at smc.vnet.net
  • Subject: [mg37596] Re: indeterminate expression
  • From: Tom Burton <tburton at brahea.com>
  • Date: Wed, 6 Nov 2002 06:53:17 -0500 (EST)
  • References: <aq874p$e6e$1@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

On 11/5/02 2:39 AM, in article aq874p$e6e$1 at smc.vnet.net, "MH"
<petronius at myrealbox.com> wrote:

> Hi, as part of a long combinatoric code, I need to calculate lots of p^n
> values.  The problem arises when p=n=0.  Such an expression is indeterminate
> obviously, but since it is part of a probability calculation, the
> probability that something with 0 probability occuring 0 times is 1.  Is
> there a rule that I can specify that would allow me to replace this
> indeterminate express with the answer that I want?  I could go back and
> change every instance where this pops up with a function or take the limit,
> but I wanted to check if there was a more efficient method.

The rule is easy,

r = HoldPattern[0^0] -> 1

once you know about HoldPattern. Preventing premature evaluation may be more
difficult. Example:

expr = Hold[2^1+3^4+0^0+1^3]

ReleaseHold[expr /. r]

Tom Burton


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