> The Maxima user documentation for genfact doesn't mention
> that it applies entier to the middle argument. (I'll
> file a report.) I think commercial macsyma changed this
> from entier to ceiling. Do we want ceiling too? The
> Maxima documentation says that x !! may differ from
> standards for non-integer x. What is the canonical
> reference for the double factorial function?
I'm not very comfortable with either floor or ceiling --
if it's not clear what is the right interpretation,
it seems best to reserve judgement and just return
an unevaluated expression. That's a policy that is often
followed (though not always) in Maxima.
That said, I'm pretty sure we can choose an entirely
new definition for genfact if we want. I don't think
there are any tests for it, and I don't think it's called
by any other code. I don't know what is a suitable
reference for genfact.
For what it's worth,
Robert Dodier