One thing I like about the 35s (and my first HP, the 34C) is the combined factorial and Gamma-function. One might think that a few multiplications to get 50! or 100! will be executed in almost no time while on the other hand evaluating a Gamma-function may take some time. So I was quite astonished when I noticed this:

- 100! and 101! take about one second. However, 100.5! (i.e. Gamma(101.5)) is returned about twice as fast in just half a second.

- 150! takes roughly 1.5 seconds - but 200! appears almost instantly.

However, the more interesting part is the obvious switch between two different algorithms that seems to take place near x=158 since 158! is slow while 159! is much faster.

The 35s seems to use a different method for factorials and the Gamma-function - which sounds quite obvious. The Gamma-algorithms seems to be somewhat faster. Which leads to the question why the 35s doesn't use this faster method for factorials as well.

Maybe someone out there can shed some light on all this. Or at least we can speculate a bit about what's going on here. :-)

Dieter