Functions and Types

(1+) (define member
  {A --> (list A) --> boolean}
  _ [] -> false
  X [X | _] -> true
  X [_ | Y] -> (member X Y))
(fn member) : (A --> ((list A) --> boolean))

(2+) (define square
  {number --> number}
  X -> (* X X))
(fn square) : (number --> number)

(3+) (define swap
  {(A * B) --> (B * A)}
  (@p X Y) -> (@p Y X))
(fn swap) : ((A * B) --> (B * A))

(4+) (define unit-vector?
 {(vector A) --> boolean}
 (@v _ <>) -> true
      _ -> false)
(fn unit-vector?) : ((vector A) --> boolean)

(5+) (define unit-string?
  {string --> boolean}
  (@s _ "") -> true
  _ -> false)
(fn unit-string?) : (string --> boolean)

(6+) (member 1 [1 2 3])
true : boolean

(7+) (square 4)
16 : number

(8+) (swap (@p 1 2))
(@p 2 1) : (number * number)

(9+) (unit-vector? (@v 1 <>))
true : boolean

(10+) (unit-string? "a")
true : boolean