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A tiny synthetic HP41 challenge - Dieter - 12-07-2016 07:17 PM
I'm not an expert if it comes to synthetic programming on the HP41, so probably someone else here may have a better idea than me for the following little challenge.
The task: truncate a number after six or seven significant digits and normalize it to the domain 0 <= X < 1.
Some examples:
3,141592654 => 0,314159 or 0,3141592
–1,234567809 E–32 => 0,123456 or 0,1234567
9,999999999 E+99 => 0,999999 or 0,9999999
0,123456 => 0,123456
Here's my solution:
Code:
CLA
ABS
STO M
ASTO M
ASTO M
ASTO M
>"\x00\x09\x99"
RCL M
CLA
ENDThe append command adds three bytes (decimal 0, 9, 153 or hex 00, 09, 99) to clear the last three digits and set the exponent to –1.
I am sure you can do better. So what's your idea here?
Dieter
RE: A tiny synthetic HP41 challenge - hth - 12-08-2016 06:25 PM
I am not good at synthetics at all. Your solution looks clever, but I think it will not handle the case when X is 0 properly. I also think you can just remove the last CLA, there is no need to clean up.
Håkan
RE: A tiny synthetic HP41 challenge - Dieter - 12-08-2016 06:46 PM
(12-08-2016 06:25 PM)hth Wrote: I am not good at synthetics at all. Your solution looks clever, but I think it will not handle the case when X is 0 properly.
Thank you for your reply. Of course the code works for x=0. A look at the M-register shows what it does. Assume x=pi.
Code:
CLA 00 00 00 00 00 00 00
STO M 03 14 15 92 65 40 00
ASTO M 10 03 14 15 92 65 40
ASTO M 10 10 03 14 15 92 65
ASTO M 10 10 10 03 14 15 92
>"000999" 10 10 10 03 14 15 92 00 09 99
...-- N ---> <--- register M --->
RCL M => 3,141592000 E-1
= 0,3141592I hoped for an elegant method of shifting the value by a nybble (half a byte) so that also results with 4, 6 or 8 digits become possible. Or something more elegant than three ASTO commands. ;-)
(12-08-2016 06:25 PM)hth Wrote: I also think you can just remove the last CLA, there is no need to clean up.
I should have known this 40 years ago: "No, Mom, my room is OK this way. Håkan said there is no need to clean up". ;-)
Dieter
RE: A tiny synthetic HP41 challenge - hth - 12-08-2016 08:34 PM
(12-08-2016 06:46 PM)Dieter Wrote: Thank you for your reply. Of course the code works for x=0. A look at the M-register shows what it does. Assume x=pi.
Code:
CLA 00 00 00 00 00 00 00
STO M 03 14 15 92 65 40 00
ASTO M 10 03 14 15 92 65 40
ASTO M 10 10 03 14 15 92 65
ASTO M 10 10 10 03 14 15 92
>"000999" 10 10 10 03 14 15 92 00 09 99
...-- N ---> <--- register M --->
RCL M => 3,141592000 E-1
= 0,3141592
If you have 0 as input and you append the 999 exponent at the end, then RCL M will put a non-normalized number in X?
(12-08-2016 06:46 PM)Dieter Wrote:(12-08-2016 06:25 PM)hth Wrote: I also think you can just remove the last CLA, there is no need to clean up.
I should have known this 40 years ago: "No, Mom, my room is OK this way. Håkan said there is no need to clean up". ;-)
Dieter
LOL!
Håkan
RE: A tiny synthetic HP41 challenge - Dieter - 12-08-2016 09:17 PM
(12-08-2016 08:34 PM)hth Wrote: If you have 0 as input and you append the 999 exponent at the end, then RCL M will put a non-normalized number in X?
Ah, OK, that's of course correct. But the next operation or a STO/RCL should normalize it.
You can also do it within the routine. For instance by adding zero, like it's done in "MT" of the PPC ROM:
Code:
CLA
ABS
STO M
ASTO M
ASTO M
ASTO M
>"\x00\x09\x99"
CLX
ST+ M
X<> M
CLA
ENDStill including a final CLA for cleanup. ;-)
Dieter