[Haskell-cafe] C++ interface with Haskell
qdunkan at gmail.com
Sat Apr 19 12:30:43 EDT 2008
> you mean, you hack around with the internal representation of those
> structures? Well, if you want to avoid double-copying, C++ can't access
> Haskell sequences, and Haskell can't access C++ sequences, I guess I don't
> see an alternative.
I don't really mind double copying, but having to declare c variants
(i.e. no stl) of all the c++ structures and then copy from one to the
other is a little tedious. I was hoping there was some clever trick
to make that easier...
> > Passing back to haskell is easier since I can use "&*vec.begin()",
> > which according to the internet should be safe because STL guarantees
> > that vector contents are contiguous.
> safe until either:
> the vector's contents change, if Haskell is assuming it's immutable,
Well, naturally I peekArray before letting c++ have it back.
> > I'm only saved by the fact that I don't have that many different kinds
> > of classes to pass. This would be much more drudgery if I had more.
> > Does anyone have a better solution or convention for marshalling c++
> > objects?
> not "better", but, you could wrap the methods of the class and call back
> into C++ (through C wrappers) to do anything with the class, if it suited
> your purposes better and wasn't too slow
Yeah, I was thinking of that, but it seemed like even more of a
hassle. However, a more practical variant might be to write a haskell
interface to marshal to vectors and strings, probably involving some
void pointer sketchiness since naturally template types can't be
expressed in a C function signature, and then poke those into the
struct when I pass it. That would only work for vectors stored by
pointer of course.
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