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Mathematica Journal: One Liners

  • To: mathgroup at
  • Subject: Mathematica Journal: One Liners
  • From: ilan at (ilan vardi)
  • Date: Mon, 27 Apr 92 00:47:31 -0700
  • Cc: wri-tech

In the new issue of the Mathematica Journal, One Liners, there is a
program called DigitalRoots which gives the result of iterating the
sum of the digits of an integer. 

 The code given there was 

DigitalRoots[n_]:= FixedPoint[(Plus @@ IntegerDigits[#])&, n]

I have discovered the following more efficient program to compute this:

MyDigitalRoots[n_]:= Mod[n, 9]

There was also a program to reverse the digits of a number:

Module[{m = IntegerDigits[n], i},
       Table[10^i, {i, 0,Length[m]-1}], m]

My program (which only takes One Line) is:

MyReverseInteger[n_]:= Fold[#1 10 + #2&, 0, Reverse[IntegerDigits[n]]]

-Ilan Vardi

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