> Do you know any common shared library that offers some kind of cosine function
> that takes a C array of doubles as input? ;) I kinda needed that to show how
> the `ndpointer` ctypes thing works.

OK, I am starting to understand the logic. Sorry for being slow.

I am looking at the setup.py of numpy/numpy/core, and it seems to me that
what you are looking for is config.add_library where config is a 
numpy.distutils.misc_util.Configuration object.