From: Tim Hunter <cyclists@...>
Date: 2003-12-10T08:12:00+09:00
Subject: Re: passing a func to a ruby func

On Wed, 10 Dec 2003 03:29:56 +0900, Elias Athanasopoulos wrote:

> On Wed, Dec 10, 2003 at 12:29:36AM +0900, ts wrote:
>> >>>>> "e" == elathan  <elathan@phys.uoa.gr> writes:
>> 
>> e> Can I export a function such as qsort() of the Linux stdlib to a
>> Ruby e> method. qsort() takes a C function pointer as a parameter.
>> 
>>  Not really understood what you want to do, but for qsort a stupid
>>  example
> 
> Well, I am trying to create a ruby method call for a C++ method which
> takes as an argument a pointer to a user-defined function. I.e. the C++
> method is like:
> 
>     foo (int a, int b, double (*f) (double *, double *), int c);
> 
> Thanks for you qsort() example. I'll try to study it and see what I can
> get from. My main worry, is that the 'f' function which is passed in
> foo() above might be more complicated than a common Ruby block.
> 
> Regards,

Presumably `foo' calls the function pointed to by `f' and you want `f' to
point to a Ruby method. The way to do this is to write an intermediate C
function `func'. Pass `func's address to `foo'. When `foo' calls `func',
`func' translates the C arguments to Ruby objects and calls the
appropriate Ruby method via rb_funcall or something. Or, `func' could call
a user-supplied Proc object. `func' can in turn convert the value returned
from whatever it calls to a C type and then return that value to `foo'.