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MathGroup Archive 2007

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Re: Re: Number of Differing Digits & Another

  • To: mathgroup at smc.vnet.net
  • Subject: [mg76387] Re: [mg76340] Re: [mg76310] Number of Differing Digits & Another
  • From: Bob Hanlon <hanlonr at cox.net>
  • Date: Mon, 21 May 2007 05:58:13 -0400 (EDT)
  • Reply-to: hanlonr at cox.net

If you allow negative numbers, the greater number does not necessarily have the greater number of digits. That's why I determined the length from Max[Abs[a,b]]


Bob Hanlon

---- DrMajorBob <drmajorbob at bigfoot.com> wrote: 
> Clear[bitDifference]
> bitDifference[a_, a_] = 0;
> bitDifference[a_, b_] /; a > b :=
>   Block[{one = IntegerDigits[a, 2], two},
>    two = IntegerDigits[b, 2, Length@one];
>    Plus @@ Abs[one - two]
>    ]
> bitDifference[a_, b_] := bitDifference[b, a]
> 
> Bobby
> 
> On Sun, 20 May 2007 01:23:41 -0500, Bob Hanlon <hanlonr at cox.net> wrote:
> 
> > Since you intend to count the bit differences your function needs to be  
> > modified to
> >
> > Clear[BitDifferences];
> > BitDifferences[a_,b_,n_]:=
> >     n-Count[Equal@@@
> >           Thread[{IntegerDigits[a,2,n],IntegerDigits[b,2,n]}],True];
> >
> > t1=Table[BitDifferences[a,b,6],{a,-16,16},{b,-16,16}];
> >
> > I would use
> >
> > Clear[BitDifferences];
> > BitDifferences[a_,b_]:=Module[
> >       {n=Length[IntegerDigits[Max[Abs[{a,b}]],2]]},
> >       n-Count[IntegerDigits[a,2,n]-IntegerDigits[b,2,n],0]];
> >
> > t2=Table[BitDifferences[a,b],{a,-16,16},{b,-16,16}];
> >
> > t1==t2
> >
> > True
> >
> >
> > Bob Hanlon
> >
> > ---- VenDiddy at gmail.com wrote:
> >> I just purchased a copy of Mathematica and I've been learning it for
> >> about a week now. You can expect that I will be posting a lot of
> >> questions. One thing I've noticed is that there are so many different
> >> ways to do the same thing!
> >>
> >> Here is a function I came up with that calculates how many binary
> >> digits two numbers differ in:
> >>
> >> BitDifferences[a_, b_, n_] :=
> >>  Count[Equal @@@
> >>    Thread[{IntegerDigits[a, 2, n], IntegerDigits[b, 2, n]}], True]
> >>
> >> For example 5 = 101 differs from 6 = 111 by one digit (the middle
> >> digit).
> >>
> >> I want to see how you would do it so I can broaden my Mathematica
> >> perspective.
> >>
> >> Thanks.
> >>
> >>
> >
> >
> >
> 
> 
> 
> -- 
> DrMajorBob at bigfoot.com



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