First, consider lists where all list items are the same time. I already know that this isn't possible the easy way due to nested polymorphic functions:
(map values '(5 6 7)) /!\ Type Checker: Polymorphic function `map' could not be applied to arguments
and I have to (inst values) to make it work:
(map (inst values Integer) '(5 6 7 8)) - : (Pairof Integer (Listof Integer)) '(5 6 7 8)
My real question is about mixed type lists. This is the shortest code that I could come up that maps the list while remembering the type of each list item. Notice how on this one I don't need to (inst values), instead, I have to type the input as (List a ...):
((lambda #:forall (a ...) ([xs : (List a ...)]) (map values xs)) '(5 a "s")) - : (List Positive-Byte 'a String) '(5 a "s")
Is there a way to do this that's more intuitive/requires fewer keystrokes? I've played around a fair bit and I can't find a shorter version. It would be okay if I could turn this into a macro, but I can't figure out how to do that either, because
... has special meaning in define-syntax-rule.
I don't want to use (inst values Any) because it would turn my list into (Listof Any), which forgets the list's length and the type of each item.