namespace Sanchime.Algrithm.Sort
[<AutoOpen>]
module Merge =

    let rec msort sorted = function
        | [] -> []
        | [x] -> [x]
        | list -> 
            let evens, odds = divde list
            in merge sorted (msort sorted evens, msort sorted odds)

    and merge sorted = function
        | xs, [] -> xs
        | [], ys -> ys
        | x::xs, y::ys ->
            if sorted y x then y::(merge sorted (x::xs, ys))
            else x::(merge sorted (xs, y::ys))
        
        
    and divde = function
    | [] -> [], []
    | x::xs ->
        let odds, evens = divde xs
        in x::evens, odds


    // let rec msort sorted = function
    //     | [] -> []
    //     | [x] -> [x]
    //     | xs ->
    //         let half = xs.Length / 2
    //         let left, right = List.splitAt half xs
    //         merge sorted (msort sorted left) (msort sorted right) 

    // and merge (sorted: 'a -> 'a -> bool) left right =
    //     let rec aux continuation left right = 
    //         match left, right with
    //         | left, [] -> continuation left
    //         | [], right -> continuation right
    //         | x::xs, y::ys ->
    //             if sorted x y then 
    //                 aux (fun acc -> continuation (x::acc)) xs right
    //             else 
    //                 aux (fun acc -> continuation (y::acc)) left ys
    //     aux id left right