Algorithmique des structures de données arborescentes 2017-2018

Bonjour, je ne comprends pas d’où viens mon erreur pour la fonction parameters,

Échec sur les arguments suivants:
Empty
voici mon code:

let rec height t =
  match t with
    Empty -> (-1)
  |Bin (x,g,d) ->  1+max(height g) ( height d)
 
let arity t=
  match t with
    Empty->(-1)
   |Bin(x,g,d)->match (g,d) with
                  (Empty,Empty)->0
                 |(Empty,_)->1
                 |(_,Empty)->1
                 |(_,_)->2

let rec arity2 t =
    match t with
    Empty -> 0
    | Bin(x,left,right) -> if arity t = 2
                            then 1 + arity2 left + arity2 right
                            else 0 + arity2 left  + arity2 right
 
   
let rec arity1 t =
    match t with
    Empty -> 0
    | Bin(x,left,right) -> if arity t = 1
                            then 1 + arity1 left + arity1 right
                            else 0 + arity1 left  + arity1 right
 
let rec size tree =
  match tree with
    Empty -> 1
   |Bin(x,left,right)->1+(size left) + (size right)
  
let rec internal t =
   match t with
   Empty -> 0
   |Bin(x,left,right) -> 1+ internal left + internal right


let  nb_leaves t = size t - internal t

let parameters t = match t with
    Empty->(size t,nb_leaves t,arity1 t,arity2 t,0)
  |_->(size t,nb_leaves t,arity1 t,arity2 t,height t)
 

Merci.