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From: jurjen@cwi.nl (Jurjen NE Bos)
Newsgroups: comp.sys.handhelds
Subject: HP28/48: Hamming weight of binary number (BITS)
Message-ID: <3053@charon.cwi.nl>
Date: 1 Mar 91 13:28:04 GMT
Sender: news@cwi.nl
Organization: STORC, Veldhoven
Lines: 17
Originator: jurjen@lijster.cwi.nl


Everybody who has had a HP16 knows that it sometimes is very convenient to
compute the number of 1 bits in a number.
Computing this on a HP28 or HP48 seems to take some time.  A recent discussion
in comp.arch yielded a much more efficient solution.  I changed it a little
bit to make it work for 64 bits, and translated it into RPL.  The program is
shown below.
Happy Hacking!

BITS:
\<< # 7777777777777777h OVER SR OVER AND
  DUP2 SR AND ROT OVER SR AND + + -
  DUP SR SR SR SR + #F0F0F0F0F0F0F0Fh AND
  #FF DUP2 / * -
\>>

I leave proving that this works as an exercise to the reader :-)