Handling branch cuts for hypergeometric functions

Raymond Toy  writes:

> These kinds of things always reminds of an example given in Kahan's
> paper Much Ado about Nothing's Sign.  He has an example two fairly
> complicated functions and asks if they're equal.  If you plug some
> random values, they are equal.  I think that if you do some naive
> manipulations, you'll prove that they are equal.  In fact, they are
> equal, except for in a small oval region of the plane, which you'd
> probably not find by random testing.  The difference arises because of
> the branch cuts of the functions involved.

But the `typical values' select only the premises of an implication,
say

   f=g => some result

It's still up to the user to work out if f=g is satisfied or not.

At least this is how I understand Albert Reiner's proposal in this
thread.

Wolfgang