compact-annotations

Documentation

A Typed Racket package for writing compact polymorphic (and non-polymorphic) function annotations with a syntax similar to that of Haskell's type annotations.

Examples:

(require compact-annotations)

(:: flip A B => A -> (A -> B) -> B)
(define ((flip v) f)
  (f v))

(:: zip-with A B C => (A B -> C) -> (Listof A) (Listof B) -> (Listof C))
(define ((zip-with zipper) as bs)
  (map zipper as bs))

(:: compare-as A B => (A A -> Boolean) -> (B -> A) -> B B -> Boolean)
(define (((compare-as base-compare) convert) v1 v2)
  (base-compare (convert v1) (convert v2)))

(:: string-shorter? String String -> Boolean)
(define string-shorter?
  (((inst compare-as Real) <) string-length))

(:: in-range? Real Real + Boolean -> Real -> Boolean)
(define ((in-range? low high [include-endpoints? #t]) x)
  ((if include-endpoints? <= <) low x high))

(:: and? A => * (A -> Boolean) -> A -> Boolean)
(define ((and? . ps) a)
  (andmap (λ ([p : (A -> Boolean)]) (p a)) ps))

To install, run raco pkg install compact-annotations.