-let rec tweight (t: T) on t: nat \def match t with [(TSort _) \Rightarrow (S
-O) | (TLRef _) \Rightarrow (S O) | (THead _ u t0) \Rightarrow (S (plus
-(tweight u) (tweight t0)))].
+rec definition tweight (t: T) on t: nat \def match t with [(TSort _)
+\Rightarrow (S O) | (TLRef _) \Rightarrow (S O) | (THead _ u t0) \Rightarrow
+(S (plus (tweight u) (tweight t0)))].