http://golangtutorials.blogspot.de/2011/06/inheritance-and-subclassing-in-go-or.html
http://stackoverflow.com/questions/1727250/embedding-instead-of-inheritance-in-go
That would allow to embed C objects in Nim Objects, and make the later compatible to C libraries.
(Araq was talking about delegates some time ago, I did not understand the term at that time...)
Converters may be able to simulate delegation, but for a large OO C library one would use thousands of converters.
(Nim RadioButton -> C RadioButton, C ToggleButton, C Button, C Bin, C Widget, C GObject...)