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The X-Philes Number 1 (1995).iso
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1995-03-31
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25 lines
(Comp.sys.handhelds)
Item: 2277 by jurjen at cwi.nl
Author: [Jurjen NE Bos]
Subj: HP28/48: Hamming weight of binary number (BITS)
Date: Fri Mar 01 1991
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 :-)