Hi, On Mon 01 Mar 2010 15:18, l...@gnu.org (Ludovic Courtès) writes:
> With ‘(system foreign)’, C pointers are mapped to Scheme foreign > objects, regardless of the type of object pointed to. Thus, to get > disjoint types in Scheme, foreign objects would need to be boxed in > structs (since structs are the only way to create disjoint types from > Scheme). > > If this analysis is correct It is > the resulting code may be somewhat > inefficient since we end up boxing C pointers twice. Do you think this is an issue? We could add an extra word to foreign pointers to make them have a type tag; or we could change the foreign pointer representation to have a vtable. The downside with that is that you can't allocate static foreign pointers that way. I have a feeling that "double-wrapping" will perform fine. I figure a high-level FFI will wrap these primitive foreign pointers in such a way that they can preserve typing information, and hide the primitive foreign pointer (if appropriate). But I could be wrong about that! Cheers, Andy -- http://wingolog.org/
