[Gretl-devel] some explanation of hyp2f1() needed

Hi again, I think the built-in hyp2f1() function needs some more documentation in the function reference, where it basically just says that it's the Gauss hypergeometric function with four arguments, and that the fourth argument should be real-valued. For example, on Wikipedia (https://en.wikipedia.org/wiki/Hypergeometric_function) it becomes relatively clear that this fourth argument should have modulus less than one. If this is actually correct, then I think it wouldn't hurt to add this to the docs. There's also more things that are not so clear: Wikipedia says "It is undefined (or infinite) if c equals a non-positive integer", but using a call with a negative integer like hyp2f1(-1,-2,-3, 0.4) yields a finite result 0.73333. I'm sure there's just a mis-interpretation on my side, but again, that's why I think some more basic remarks in the function ref would be needed. thanks sven