Date:         Mon, 25 Jun 2001 22:09:50 -0400
Reply-To:     Richard DeVenezia <radevenz@IX.NETCOM.COM>
Sender:       "SAS(r) Discussion" <SAS-L@LISTSERV.UGA.EDU>
From:         Richard DeVenezia <radevenz@IX.NETCOM.COM>
Organization: MindSpring Enterprises
Subject:      Re: Count the '1's in a binary number?

Ya:

Here is a data step that counts the number of on bits and creates a bit
string

data _null_;
 n = 13;

 mask = 8000x;
 nBitsOn = 0;
 length bitString $32;  * left side msb;
 strIndex = 1;

 do while (mask ne 0);
   if band (n, mask) ne 0 then do;
     nBitsOn ++ 1;
     subStr (bitString, strIndex) = '1';
   end;
   else
     subStr (bitString, strIndex) = '0';

   mask = brshift ( mask, 1 );
   strIndex ++ 1;
 end;

 put n= nBitsOn= bitString=;
run;
--
Richard DeVenezia - SAS Macros and AF Tools
http://www.devenezia.com

"Droogendyk, Harry" <Harry.Droogendyk@CIBC.COM> wrote in message
news:F0161D3F7AC5D411A5BE009027E774D6014E8ECF@GEMMRD-SCC013EU...
> Not one line, but it does as you want.
>
> data _null_;
>
>     number = 13;
>     power  = 9999999;
>     cnt    = 0;
>     do while ( number > 0 and power > 0);
>          cnt ++ 1;
>          power  = int(log2(number));
>          number = number - ( 2 ** power );
>      end;
>      put cnt=;
> run;
>
>  -----Original Message-----
> From: Huang, Ya [mailto:ya.huang@AGOURON.COM]
> Sent: June 25, 2001 5:15 PM
> To: SAS-L@LISTSERV.UGA.EDU
> Subject: Count the '1's in a binary number?
>
>
>
> Hi there,
>
> Suppose I have a positive integer number and I want to count the number of
> '1's in the number presented with a binary format, for example, 13 is
> '1101' in binary, so the number of '1's = 3. I wonder if there is a way
> I can count it without first converting to character string then use
> compress() etc.? In other word, I need a pure mathematical algorithm,
better
>
> to be a one line solution. My instinct says that should be not very
> difficult,
> but I can't figure it out at the moment.
>
> Thanks
>
> Ya Huang