Callbacks for external libraries

Hello there,
I am wondering if it is possible to use external libraries that exhibit a callback interface. Has anybody some sample code that shows how to do this?
Many thanks in advance,
-Tom

Well, I don't know what you means for external libraries with callback interface, because you can:

call external rebol files, so you create one or more "externaLib.r" file like:

Code:

Rebol [title "externaLib"]
myspecialfunc: func [ a b] [ a + b]

and you can call it/them in the main program:

Code:

do %externaLib.r
total: myspecialfunc 5 17

OR you can call external programs:

Code:

call/wait  "pdftohtml   myfile "

These are some examples..

See rebgui at http://www.dobeash.com/rebgui.html for more information about external libraries

MaxV,
thanks for the quick response, and sorry that I wasn't clearer.
I am rather talking about an external dll which, if I was using it with C, provides me functions that take a pointer to a callback function. Would that dll be usable from within REBOL without using any additional C layer or something?
Thanks,
-Tom

Absolutely, that's a hot topic right now: http://www.rebol.com/r3/notes/callbacks.html

Guys,
thank you very very much for your feedback.
Regards,
-Tom