[Cython] python callback

[Gabriel Gellner]

On Sat, Apr 05, 2008 at 12:58:21PM -0400, simon at arrowtheory.com wrote:
> > Could anyone give me a tip on how to convert a python function
> > of the form
> >
> > def func(x):
> >     return some_operation(x)
> >
> > to a C function of the form
> >
> > cdef void cfunc(double x, double *y):
> >     y = some_operation(x)
> 
> y[0] = some_operation(x)
> 
Yeah, sorry that was a typo...

> >
> > That is I want to be able to turn a python function into
> > a C function with pass by reference return semantics.
> >
> > I looked at the cheesefinder example, and I am not sure how to adapt it,
> > as I
> > want to be able to have the user supply the python function, and I can't
> > think
> > of how to make a cdef callback function that knows what this function is,
> > that
> > is
> >
> > cdef void callback(souble x, double *y):
> >     y = func(x)
> >
> > I am not sure how to set func in this way, without rewriting the cdef each
> > time. In python I would just use a higher order function . . .
> 
> in general, you need an extra "void *" argument in the callback
> function (which you would use to pass a python callable).
> Well designed C libraries use this convention, but it
> sounds like you don't have this.
> 
Curses, I guess I will have to change the original code :-(

Thanks for the help.

Gabriel