Following code snippet shows how to compute bound (i.e the min and max elements) of a List using F#.
| let rec bound (lst:int list) : (int*int) option = | |
| match lst with | |
| | [] -> None // Empty List | |
| | xhd::xtl -> | |
| match bound xtl with | |
| | None -> Some (xhd,xhd) // List with only 1 element | |
| | Some (x,y) -> | |
| Some ((if x>xhd then xhd else x), (if y<xhd then xhd else y)) | |
Solution outlined here is quite trivial and use the pattern matching facilities of F#. In case of an empty list (line 3), it returns None; otherwise, it returns the bound as Some (int*int) (line 8).
Therefore, the signature of bound is given by-
| val bound : lst:int list -> (int * int) option |
Output of bound –
| > bound [1;2;3;4];; | |
| val it : (int * int) option = Some (1, 4) | |
| > bound [1];; | |
| val it : (int * int) option = Some (1, 1) | |
| > bound [];; | |
| val it : (int * int) option = None |
