Re: [office-formula] FACT/FACTDOUBLE with fractions

["David A. Wheeler" <dwheeler@dwheeler.com>]

> > FACT and FACTDOUBLE have
> > 
> > | TBD: Should we mandate that it compute INT() first? Excel 2002 computes
> > | the INT() of the parameter first, and then computes the factorial. It'd
> > | be more flexible if we allowed fractional values. This has been reworded
> > | to note that it's only REQUIRED to support integer parameters, and then
> > | permitting GAMMA() for fractional values.
> > 
> > For interoperability we should not allow fractionals. Opinions?


Sortof agree.  For interoperability, I think we should require INT be applied to the operation first.  I believe most applications do that.  If you don't want INT applied, use GAMMA.

> > Btw, which applications do support GAMMA?
> 
> Gnumeric implements GAMMALN, the natural logarithm of the Gamma
> function. So if GAMMA would be defined in OpenFormula we would have
> GAMMA in short order.

GAMMA is already in OpenFormula.  I don't recall if that's in an existing spreadsheet application, but it's obviously a standard and widely-known mathematical function, and it's  essentially a universally-defined operation in computer algebra and mathematical systems (Maxima, Octave, etc.).  It's also pretty trivial to implement (e.g., if you already have GAMMALN).

As long as there is a GAMMA, then we can say that "FACT always does an INT first" without anyone being able to complain that we've lost capability.

--- David A. Wheeler