Well, I thought that type is the way to define arbitrary predicate for checking the function argument. That's why I've got confused. But it's really over my head now, thank you for the link nevertheless.
Ramarren wrote:Well, there is something called filtered-dispatch, which allows dispatching on arbitrary predicates, but I am not sure how widely it is used, if at all.
I just realized that CFFI uses something very similar to filtered-dispatch. I guess this could also be used to make those defoptimizer's of SBCL portable (unless those which use SBCL's internals, of course).