> Calls from ocaml to C are very cheap. If your access function doesn't
> do any allocation (i.e. never calls the GC), you can even make it
> faster by marking it as "noalloc". Beware many functions do
> allocate, including copy_double or copy_string.

Is this a special annotation for the external keyword? A quick glance
over the ocaml manual doesn't show up anything.

Jonathan