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MathGroup Archive 2006

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Re: Problem with using /.

  • To: mathgroup at smc.vnet.net
  • Subject: [mg69246] Re: Problem with using /.
  • From: "Nag" <Naga1010 at gmail.com>
  • Date: Sun, 3 Sep 2006 23:46:33 -0400 (EDT)
  • References: <edadil$pd0$1@smc.vnet.net><eddqil$3uh$1@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Peter Pein wrote:
>
> Hi Nag,
>
> you try to assign a value to Sum[...]; this becomes Set[Sum[...],0] --
> but Sum is a Protected function. Furthermore, Set is not Rule.
>
> I guess you wanted:
>
> M[j_, t_, k_] := FullSimplify[D[MGF[t, k], {t, j}] /. u -> 0,
>      Sum[Subscript[p, i], {i, 0, k}] == 1];
>
> You can use Simplfy instead of FullSimplify too.
>
> Peter

Hi Peter:

The = was a typo. It should have been a  ->
With  -> there is no error but the substitution doesn't happen.
The substitution works when I use == as you suggested.

Why does -> not work but == work?

Thanks
Nag


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