[Numpy-discussion] ufunc void *extra

[Robert Kern]

On Sat, Aug 22, 2009 at 18:15, Marty Fuhry<martyfuhry at gmail.com> wrote:
> The "Beyond the Basics" manual
> (http://docs.scipy.org/doc/numpy/user/c-info.beyond-basics.html)
> indicates that the generic ufunc loop (in this example loop1d) has a
> void* extra (or void* data) argument that can be used to pass extra
> data to the ufunc, but it doesn't indicate how to use this argument.
>
> Can anyone tell me how to use this extra argument? I'm trying to get a
> ufunc to perform a different operation by passing it a second
> parameter, but I'm not sure how to do this.
>
>>>> some_ufunc(narray, "A")
> will perform operation A on object narray
>>>> some_ufunc(narray, "B")
> will perform operation B on object narray
>
> Is this even a valid operation?

No. This is not configurable at call-time and certainly not from
Python. It is used only from the C level. In particular, it is used
for things like the ufuncs in scipy.special to configure the
(otherwise generic) ufuncs with the function pointer that does the
actual computation.

-- 
Robert Kern

"I have come to believe that the whole world is an enigma, a harmless
enigma that is made terrible by our own mad attempt to interpret it as
though it had an underlying truth."
  -- Umberto Eco