Typing Lambda Calculus & Generic Function & MOP

functionaltype.carrot.scm

;;; there is no need for type Bool

(= (true  a a a)
   x y x)

(= (false a a a)
   x y y)


;;; Twisted algebraic datatype

(= (cons a (List a) (List a))
   x xs f
   (f x xs))

(= (nil a (List a))
   t
   'nil)

(= (car (List a) a)
   xs
   (xs true))

(= (cdr (List a) (List a))
   xs
   (xs false))

;;; An example of MOP.
;;; The expression `(a b)` gets applied to generic function `call` 
;;; at compile time to modify the AST.

;;`(1 + 2 + 3)`
(= (call Int (Fn Int a) a)
   i f
   (f i))

;;`(xs take 5 fold + 0)`
(= (call (List a) (Fn (List a) b) b)
   xs f
   (f xs))

(= (call (Fn a b) a b)
   f x
   (f x))