Jane Street OCaml Challenge: Higher-Order Functions

Let's define a function that adds 1 to any number:

let add1 x = failwith "For you to implement"

Now define a square function:

let square x = failwith "For you to implement"

First-Class Functions

Functions in OCaml are first-class — they can be passed around just like values.

Implement a function twice that applies a given function twice:

let twice f x = failwith "For you to implement"

Use twice to implement:

let add2 = failwith "For you to implement" (* Hint: use add1 *)

let raise_to_the_fourth = failwith "For you to implement" (* Hint: use square *)

let%test "Testing add1..." = Int.(=) 5 (add1 4)

let%test "Testing square..." = Int.(=) 16 (square 4)

let%test "Testing square..." = Int.(=) 16 (square (-4))

let%test "Testing add1..." = Int.(=) 5 (twice add1 3)

let%test "Testing add2..." = Int.(=) 1337 (add2 1335)

let%test "Testing raise_to_the_fourth..." = Int.(=) 1 (raise_to_the_fourth 1)

let%test "Testing raise_to_the_fourth..." = Int.(=) 10000 (raise_to_the_fourth 10)