let rec sumList aList =
    match aList with
    | [] -> 0
    | head :: tail -> head + sumList tail

let minList aL =
    let h = List.head aL
    let rec min aList cur =
        match aList with
        | [] -> 0
        | head :: [] -> if head < cur then head else cur
        | head :: tail -> if head < cur then min tail head else min tail cur
    min aL h

let maxList aL =
    let h = List.head aL
    let rec max aList cur =
        match aList with
        | [] -> 0
        | head :: [] -> if head > cur then head else cur
        | head :: tail -> if head > cur then max tail head else max tail cur
    max aL h

let search aL elem =
    let rec searchList aList =
        match aList with
        | [] -> false
        | head :: [] -> if head = elem then true else false
        | head :: tail -> if head = elem then true else searchList tail
    searchList aL

let firstHalf aList =
    let rec dropLast = function
        | ([] | [_]), _ -> []
        | x, ([] | [_]) -> []
        | x::xt, y::ys::yt -> x :: dropLast (xt, yt)
    dropLast (aList, aList)

let x = firstHalf [0;1;2;3;4;5;6;7]

let a = [1;2;3;4;45;6;7;8;9;0;100]

let x = sumList a       // 185

let y = minList a       // 0

let z = maxList a       // 100

let mu = search a 100   // True

let x = firstHalf [0;1;2;3;4;5;6;7]   // [0; 1; 2; 3]