26 Feb 2015

interval.ml

module type Comparable = sig
    type t
    val compare: t -> t -> int
    val to_string: t -> string
end;;

module Interval (IType: Comparable) = struct
    type endpoint = IType.t
    type interval = endpoint list
    exception WrongInterval
    let create (start: endpoint) (finish: endpoint): interval =
        if finish < start then
            raise WrongInterval
        else
            [start; finish]
    let is_empty (ii: interval): bool = List.length ii = 0
    let contains (ii: interval) (x: endpoint): bool =
        match ii with
        | [left; right] -> left <= x && x <= right
        | _ -> raise WrongInterval
    let intersect (i1: interval) (i2: interval): interval =
        match i1, i2 with
        | [left1; right1], [left2; right2] ->
            let left = max left1 left2 in
            let right = min right1 right2 in
            if left <= right then
                [left; right]
            else
                []
        | _ -> raise WrongInterval
    let to_string (ii: interval): string =
        let ris = List.map (IType.to_string) ii
        |> List.fold_left (fun acc v -> acc ^ ", " ^ v) "" in
        let ris = if String.length ris > 0 then
            String.sub ris 2 (String.length ris - 2)
        else
            ris
        in
        "[" ^ ris ^ "]"
end;;