lborg019

let rec inner xs ys =
    match xs, ys with
    | [], [] -> 0
    | [], ys -> 0
    | xs, [] -> 0
    | x::xs, y::ys -> x * y + inner xs ys;;
    (*
        The head of the first list (xs) gets multiplied
        by the head of the second list (ys).
        We add the next call to this value and recursion

lborg019

type Exp =
    | Num of int            //number of integers
    | Neg of  Exp            //negation
    | Sum  of Exp * Exp     //sum
    | Diff of Exp * Exp     //difference
    | Prod of Exp * Exp     //product
    | Quot of Exp * Exp;;   //quotient

let rec evaluate = function
    | Num n        -> Some n

lborg019

let rec split = function
    | [] -> ([], [])
    | [a] -> ([a], [])
    | a::b::cs -> let (M,N) = split cs in (a::M, b::N)

let rec merge = function
    | ([], ys) -> ys
    | (xs, []) -> xs
    | (x::xs, y::ys) -> if x < y then x :: merge (xs, y::ys)
                         else y :: merge (x::xs, ys)