CORE: type system #16

We should be able to create a minimalistic type system for lifp.

Something like:

;; [number number] -> number
(def! sum (fn (a b) (+ a b)))

Rules:

• ;; starts a type block
• -> indicates return value
• scalar types are bool number builtin nil special string any
• functions should be typed by their type signature (i.e., no closure but (number) -> number)
• lists are typed with () and their type (number) is a list of numbers
• ... means variadic arguments (NOT SUPPORTED BY RUNTIME YET)
• variadic arguments are always last (NOT SUPPORTED BY RUNTIME YET)

More examples

;; number
(def! a 12)

;; [number] -> bool
(def! pos? (fn (a) (> a 0)))

;; [(number) number] -> number
(def! nth (fn (list num) (list:nth list num)))