Question

Write a function (int_to_whole) in OCaml that converts an integer into a whole number if one exists (a whole number is 1, 2, 3, ...). Use an option type because not all integer inputs can be converted.

type whole = One | Succ of whole;;

let int_to_whole (x:int) : whole option = ...

Answer 1

type whole = One | Succ of whole;;

let rec int_to_whole (x:int) : (whole option) =

if x < 0 then None else

match x with

| 0 -> None

| _ -> let y = int_to_whole (x+1) in

match y with

| None -> None

| Some z -> Some (Succ z);;

However, this will lead to stack overflow for large x. You can resolve this problem by making it tail-recursive:

type whole = Zero | Succ of whole

let int_to_whole (x:int) : (whole option) =
if x < 0 then None else
let rec int_to_whole' (x:int) (accum:whole) : (whole option) =
match x with
| 0 -> Some accum
| _ -> int_to_whole' (x+1) (Succ accum)
in int_to_whole' x Zero;;

This OCaml code are correct .

So please any queries please tell here .

Thank you.