[Octave-bug-tracker] [bug #43551] Matlab incompatibility for gamma function for negative integer arguments

[John W. Eaton]

Follow-up Comment #2, bug #43551 (project octave):

The example that resulted in someone pointing out the change to me was one in
which gamma(x) was in the denominator of an expression inside a summation. 
Previously, these terms were then zero and not causing trouble.  With the new
behavior, they are NaN and cause trouble because then the summation is NaN as
well.

If we choose Inf as compatible with Matlab and perhaps more useful, then I
think we can still treat -0 specially.

One more question:  what is the purpose of the lines


      if (xisinf (result) && (static_cast<int> (gnulib::floor (x)) % 2))
        result = -octave_Inf;


now?  Given the current checks at the top of the function, is this condition
ever met?  And why would we make the result negative only at odd values?

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