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+--- Thread: integer logarithm on the HP-16C (/thread-21215.html)
integer logarithm on the HP-16C - richmit - 01-29-2024 04:14 AM
I use the HP-16C quite a bit, and one thing I miss is something I grew up calling the "integer logarithm". It's simply the floor of the base 2 logarithm -- equal to the index of the most significant set bit. So here is my version:
Code:
LBL A
x=0?
/
LJ
R^
1
LJ
R^
-
RTNIt runs in about 4 seconds on my original 16C and is instantaneous on the DM-16L. Note that it wipes out the entire contents of the stack. An "Error 0" is produced for a zero argument.
I'm curious how others would implement this function. My first attempt was to shift until a zero was found, but that took a LONG time to run on the original 16C.
Note you can get CTZ (Count Trailing Zeros) from this function like so:
Code:
ENTER
ENTER
1
-
NOT
AND
GSB A