q1
fun unique [] = []
    | unique (x::xs) = x:: unique (List.filter (fn y => y<>x) xs);
q3
local
    fun merge _ [] [] = []
        | merge _ list [] = list
        | merge _ [] list = list
        | merge pred (x::xs) (y::ys) = if pred(x,y) then (y::(merge pred (x::xs) ys))
                                                  else (x::(merge pred xs (y::ys)))
in
    fun mergesort _ [] = []
        | mergesort _ [x] = [x]
        | mergesort pred l = merge pred
            (mergesort pred (List.take (l,((length l) div 2))))
            (mergesort pred (List.drop (l,((length l) div 2))))
end;

local
    fun merge _ [] [] = []
        | merge _ list [] = list
        | merge _ [] list = list
        | merge pred (x::xs) (y::ys) = if pred(x,y) then (y::(merge pred (x::xs) ys))
                                                  else (x::(merge pred xs (y::ys)))
in
    fun mergesort _ [] = []
        | mergesort _ [x] = [x]
        | mergesort pred l = merge pred
            (mergesort pred (List.take (l,((length l) div 2))))
            (mergesort pred (List.drop (l,((length l) div 2))))
end;
q4
fun sublistsSort l = mergesort (fn(x,y) => length x > length y) l