Shen is a portable functional programming language by Mark Tarver. It is the successor to the award-winning Qi language, with the added goal of being highly portable across platforms.

More information is available on the official website.

(define filter
  _ []       -> []
  F [X | Xs] -> [X | (filter F Xs)] 
                where (F X)
  F [_ | Xs] -> (filter F Xs))

(define element?
  _ []      -> false
  X [X | _] -> true
  X [_ | Y] -> (element? X Y))

(define walk
  _ []      <- (fail)
  F [X | _] -> X where (F X)
  F [_ | Y] -> (walk F Y))

(define y-combinator
  F -> ((/. X (X X))
        (/. X (F (/. Y ((X X) Y))))))

(let F (freeze (output "Hello!"))
  (thaw F))

> "Hello!"

(tc +)

(define map
  {(A --> B) --> (list A) --> (list B)}
  _ []       -> []
  F [X | Xs] -> [(F X) | (map F Xs)])

(map (+ 1) ["a" "b" "c"])

> type error

(datatype maybe-type

  _____________________
    none : (maybe A);

         X : A;
  _____________________
  (some X) : (maybe A);

      M : (maybe A);
  _____________________
     (unwrap M) : A;)

(defprolog member
  X [X | _] <-- ;
  X [_ | Y] <-- (member X Y);)

(prolog?
  (member X [1 2 3])
  (member X [3 4 5])
  (return X))

> 3

(define bit?
  B -> (element? B [0 1]))

(defcc <b>
  B <b> := [B | <b>] where (bit? B);
  B     := [B] where (bit? B);)

(defmacro infix-macro
  [X + Y] -> [+ X Y]
  [X * Y] -> [* X Y])