[Numpy-discussion] Questions about C API

Russell E Owen owen at astro.washington.edu
Fri Apr 9 10:26:09 EDT 2004

I'm trying to write a median function (surely one is there already, 
but if so I've not found it). The fastest technique seems to involve 
rearranging the data in place. So I'd like to offer two calls:
- A version that rearranges the input array if no local copy needed 
to be made (e.g. the input data was already contiguous and of the 
expected type). I know how to write that one.
- A safer, slower version that always makes a copy of the input data. 
I'm stuck on that. The high-level interface has flags for when to 
make a local copy, but none of them seems to mean "always make a 
local copy". Surely I am missing something there? I guess I could get 
the data, see if a local copy was made and if not, make a copy of my 
own, but that seems messy.

Also, is there any simple sample code running around for handling 
arrays of any type (e.g. with C++ templates)? Right now I'm writing 
to a specific type (since it's easy and I know what type to expect 
for my application), but I'd rather make my code more general and 
numarray-like. I figured the numarray code itself would be a good 
example, but, well, I didn't understand the parts I looked at (maybe 
I'm clueless, maybe I didn't find the right bits to examine).

-- Russell

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