[Octave-bug-tracker] [bug #60055] regarding to bug #15872: atanh branch cut strangeness

[Rik]

Follow-up Comment #6, bug #60055 (project octave):

"What I expect about atanh(3) is the principal value (ppv) of it.
As in sqrt(4) = 2 (is the ppv)."

This is just a choice.  One could return the principal value or not return the
principal value.  There is nothing that says +2 is a better answer than -2 for
sqrt(4).

atanh in Octave is mapped to the C/C++ math library.  That library changes
very slowly so I'm surprised that you don't replicate a zero error.  tanh is
mapped to ::tanh which throws it to the linker to make a decision about which
tanh implementation to use.  It's possible that you have more than one math
library present on your system and that mixing atanh from one library with
tanh from a different library results in incomplete cancellation.  But that
does seem low probability.  I suppose you could also look at the change
history for the C/C++ math library and see if there have been any updates
touching on the hyperbolic functions.

                          

    _______________________________________________________

Reply to this item at:

  <https://savannah.gnu.org/bugs/?60055>

_______________________________________________
  Message sent via Savannah
  https://savannah.gnu.org/