mergesort list = if length list < 2
                 then list
                 else let half  = length list / 2
                          left  = take half list  # take zoberie prvych half prvkov z listu a zahodi zvysok
                          right = drop half list  # drop utrhne prvych half prvkov z listu a vrati zvysok
                      in
                          merge (mergesort left) (mergesort right)

merge [] right   = right
merge left []    = left
merge left right = if first left < first right                       # first vrati prvy prvok zoznamu
                   then cons (first left) (merge (rest left) right)  # rest vrati zvysok zoznamu okrem prveho prvku
                   else cons (first right) (merge left (rest right)) # cons prida prvok na zaciatok zoznamu