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MathGroup Archive 2000

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Re:NestWhile

  • To: mathgroup at smc.vnet.net
  • Subject: [mg23265] Re:NestWhile
  • From: "Alan W.Hopper" <awhopper at hermes.net.au>
  • Date: Sat, 29 Apr 2000 22:05:07 -0400 (EDT)
  • Sender: owner-wri-mathgroup at wolfram.com

Dear mathgroup ,


Concerning my query before Easter,  about a version 3 equivalent to
NestWhile.

Thanks to Hartmut Wolf,  Daniel Reeves,  Andrzej Kozlowski,  and
Jens-Peer Kuska
for their solutions.

And I received an e-mail from Eric Bynum of Wolfram Technical Support,
with code
which  appropriately utilizes both Nest and While.  Thanks also, Eric.


Here is Eric's  Mathematica 3 Keith Sequence solution ;


In[1]:=
 V3KeithSequence[n_Integer?Positive] :=
    Module[{d = IntegerDigits[n], l, counter, lis},
      l = Length[d];
      counter = 1;
      While[Nest[Append[#, Plus @@ Take[#, -l]] &, d, counter][[-1]] <
n,
        counter++;
        lis = Nest[Append[#, Plus @@ Take[#, -l]] &, d, counter]];
      lis
      ]

 In[5]:=
  V3KeithSequence[197]

  Out[5]=
  {1, 9, 7, 17, 33, 57, 107, 197}


Where as before,  1+9+7=17,  9+7+17=33, etc., ending again with 197.




Alan Hopper

awhopper at hermes.net.au




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