Little challenge for HP-15C experts...

[J-F Garnier]

(07-27-2024 01:47 AM)Gerson W. Barbosa Wrote:  I’m away from home and don’t have any of mine at hand, but I remember 69.5 CHS x! takes rather long to return the answer.

You have good memory !

Indeed, computing x! (gamma) of large negative (non integer) numbers can take a lot of time, and there is no 'running' message in these cases.

The largest computing time (thus blank display time) is with -99.5, with a result of zero after more than 15s !
Computing gamma of non-integer numbers less than -100 is immediate with null result.


Now, why was I seeking for long blank states, that lead me to (apparently) rediscover the x! case ?
As I reported it before, we can't see this brief blank display during key processing with the 15c CE, contrary to the 15C and even the 15c LE, and this is IMHO a small inconvenience of this model, because we have no visual feedback of keystrokes that don't change the display content.

BUT, we can detect a very brief blank state with -99.5 x! on the 15c CE.
This is a bit hard to see, but is clear when we compare the effect of -99.5 x! with -100.5 x! (the later immediately returns 0)
This proves that blank states are not completely filtered out by the firmware, and so it should be possible to have this blank state feedback for all key processing.

J-F