The game of NIM

I adapted this program for the HP41 from the original HP25 code found in a Gene Wright's page . See instructions in that page.

 
Contents of NIM25.PRG
---------------------

lbl 01
enter
int
abs
x#y?
gto 22
x=0?
gto 22
4
xSUMSUMy
x>y?
gto 22
x=y?
gto 22
rcl 01
+
chs
sto 01
xSUM0?
gto 46
x=0?
gto 46
stop
gto 25
lbl 22
rcl 00
sqrt
gto 46
lbl 25
rcl 01
1
-
x=0?
gto 48
4
/
int
4
*
1
+
x=y?
gto 40
gto 42
lbl 40
1
-
lbl 42
chs
sto 01
stop
gto 01
lbl 46
rcl 03
rtn
lbl 48
rcl 02
end
You need to enter the values 55178 in memory 03, 3507.1 in memory 02, -1 in memory 00 and (important!): -15 in memory 01. Don't forget to set the display mode to FIX 0.

Also, before you execute NIM25.PRG you must put your first turn in X: 1, 2 or 3 are valid numbers for your first turn.

In the last adaptation I tried to maintain high compatibility with original HP25 code and I didn't include special HP41 commands.

Note: The right name of this game is NIM and isn't NIMB. You can find interesting discussions about this game, for example, in:

"The Master Book of Mathematical Recreations" by Fred Schuh. (Dover Publications Inc., New York, pages 144 to 154),
"Mathematical Recreations and Essays" by W.W. Rouse Ball and H.S.M. Coxeter (Dover, pages 36 to 38),
"Mathematics and the Imagination" by Edward Kasner and James Newman (I have a Spanish translation)
and several articles written by Martin Gardner for "Scientific American".

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