Looks neat. After using J for awhile I've come to dislike the who monad/dyad thing. It must be an old Lisper thing, but I wish there was just a regular argument list and all the arguments had the same semantics.

I know in J you can used an array of boxed objects to "simulate" "normal" function definitions except that you don't get the rank behavior for those argument lists. Nothing prevents a language from having "normal" functions and also being able to support rank on each argument.