%NFACT bug

[Han]

If I am not mistaken, is flag 22 is for cases when you truly have infinity (such as division by 0), whereas flag 21 is for overflow. %NFACT does respect flag 21.

As for the second issue, it has to do with the fact at %NFACT (and pretty much any other SysRPL command) does not do any argument checking. That it works for almost any decimal value is a mere bonus due to the algorithm implemented. Basically the algorithm checks a few special cases and then proceeds with the general algorithm, which fails for the case when the input \( x \) satisfies \( x\in (-1,1) \). Perhaps you are expecting it to return the factorial of any real number, whereas the program is designed to return the factorial of an DOREAL integer.