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Re: Russian Peasant Multiplication / was question on how to do this

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  • Subject: [mg131401] Re: Russian Peasant Multiplication / was question on how to do this
  • From: d.a.paxton at gmail.com
  • Date: Wed, 3 Jul 2013 05:00:06 -0400 (EDT)
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On Saturday, June 29, 2013 2:47:03 AM UTC-6, Richard Fateman wrote:
> Dave --
>
> 1.  You should try to come up with a useful subject line
>
> in the future.
>
> 2. It is called Russian Peasant Multiplication (which you may
>
> find on Google).
>
> 3. There is no reason to believe that a procedural algorithm
>
> has a formula, but in this case I think the inverse is known
>
> as division :)

Thanks for the responses.  IntegerDigits is basically a List function.  If you pluck a number out and use it how does one then bring it back into focus?  I thought about it late last night and there may be a way to do it in base ten.  It gets messy when the starting number is below the base.

  Today I thought to just run to base two and figure it out.  Basically the number ( 13 ) is 1101.  All I have so far is to do a BitAnd of 1.  Like this.  A= BitAnd [13,1],  ( this gives a 1 as 13 is odd ) A is the drop number.  B= number ( 13 in this case ) -A.  The carry number is then B/2.  In this case 6 or 110.  So when marching down the columns of numbers in the multiply this may be the easiest way to go.  I will have to start to fit this into a matrix form and then figure out how to code the left or right diagonals.  That does not seem straight forward at this point.



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