[Numpy-discussion] arccosh for complex numbers, goofy choice of branch

Pauli Virtanen pav@iki...
Thu Jul 17 16:56:12 CDT 2008

Mon, 17 Mar 2008 08:07:38 -0600, Charles R Harris wrote:
> OK, that does it. I'm going to change it's behavior.

The problem with bad arccosh branch cuts is still present:

>>> import numpy as np
>>> numpy.__version__
>>> np.arccosh(-1e-9 + 0.1j)
>>> np.arccosh(1e-9 + 0.1j)
>>> np.arccosh(-1e-9 - 0.1j)
>>> np.arccosh(1e-9 - 0.1j)

Ticket #854. http://scipy.org/scipy/numpy/ticket/854

I'll write up some tests for all the functions with branch cuts to verify 
that the cuts and their continuity are correct. (Where "correct" bears 
some resemblance to "ISO C standard", I think...)

Pauli Virtanen

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