?

rec.ml

(* (('a * 'b as 'a) * 'b) list -> 'a *)

let rec maximum xs = 
       let aux xs = 
            match xs with 
            | [(a,b)] -> (a,b)
            | (a, b) :: xs -> 
                let (a', b') = maximum xs in
                if b > b' then 
                    (a, b)
                else  
                    (a', b')
            | [] -> failwith "max of empty"
        in
        aux xs |> fst