[Numpy-discussion] ufuncs on user-defined types in numarray

Todd Miller jmiller at stsci.edu
Fri Dec 17 07:10:12 EST 2004

On Fri, 2004-12-17 at 08:31, konrad.hinsen at laposte.net wrote:
> I am working on making ScientificPython 
> (http://dirac.cnrs-orleans.fr/ScientificPython/) compatible with 
> numarray. One problem I stumbled across is that one feature of Numeric 
> seems to be absent from numarray: the possibility to call ufuncs with 
> arguments of non-numeric types, leading to a corresponding method call.
> As an illustration, the following example works fine with Numeric, but 
> crashes with numarray:
> from Numeric import sqrt
> #from numarray import sqrt
> class DummyValue:
>      def __init__(self, string):
>          self.string = string
>      def __str__(self):
>          return self.string
>      def sqrt(self):
>          return DummyValue('sqrt(%s)' % self.string)
> x = DummyValue('x')
> print sqrt(x)
> Is this a bug or a feature? 

It's a missing feature.

> Is there another way to make ufuncs work with user-defined classes and types?

Not that I know of.  How critical a feature is it?  Do you have a work around?

numarray ufunc handling is in flux as I'm adding numarray support to
scipy.  At some point,  there's going to be a major ufunc consolidation,
and perhaps I can add this additional feature then.


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