Using higher order and anonymous functions in ML

	fun increment_n_times (n,x) = (* computes n + x *)
	if n=0
	then x
	else 1 + increment_n_times(n-1,x)
	fun double_n_times (n,x) = (* computes 2^n * x *)
	if n=0
	then x
	else 2 * double_n_times(n-1,x)
	fun nth_tail (n,xs) = (* example 3,[4,8,12,16] -> [16] *)
	if n=0
	then xs
	else tl (nth_tail(n-1,xs))
	(* n_times is a higher-order function which takes a function, an int and a value and
	it's signature is ('a -> 'a) * int * 'a -> 'a
	*)
	fun n_times (f,n,x) =
	if n=0
	then x
	else f (n_times(f, n-1,x))
	fun increment x = x +1
	fun double x = x + x
	val x1 = n_times(double,4,7)
	val x2 = n_times(increment,4,7)
	val x3 = n_times(tl, 2, [4,8,12,16])
	fun addition (n,x) = n_times(increment, n, x)
	fun double_n_times (n,x) = n_times(double,n,x)
	fun nth_tail(n,xs) = n_times(tl, n, xs)
	(* example of using an anonymous function *)
	fun triple_n_times (n,x) = n_times((fn x => 3 *x),n,x)
	(* output of program
	- use "higherorder.sml";
	[opening higherorder.sml]
	val increment_n_times = fn : int * int -> int
	val double_n_times = <hidden-value> : int * int -> int
	val nth_tail = <hidden-value> : int * 'a list -> 'a list
	val n_times = fn : ('a -> 'a) * int * 'a -> 'a
	val increment = fn : int -> int
	val double = fn : int -> int
	val x1 = 112 : int
	val x2 = 11 : int
	val x3 = [12,16] : int list
	val addition = fn : int * int -> int
	val double_n_times = fn : int * int -> int
	val nth_tail = fn : int * 'a list -> 'a list
	val triple_n_times = fn : int * int -> int
	val it = () : unit
	*)

view raw gistfile1.sml hosted with ❤ by GitHub