src/HOL/Data_Structures/RBT_Map.thy

 fun del :: "'a::linorder \<Rightarrow> ('a*'b)rbt \<Rightarrow> ('a*'b)rbt"
 and delL :: "'a::linorder \<Rightarrow> ('a*'b)rbt \<Rightarrow> 'a*'b \<Rightarrow> ('a*'b)rbt \<Rightarrow> ('a*'b)rbt"
 and delR :: "'a::linorder \<Rightarrow> ('a*'b)rbt \<Rightarrow> 'a*'b \<Rightarrow> ('a*'b)rbt \<Rightarrow> ('a*'b)rbt"
 where
 "del x Leaf = Leaf" |
-"del x (Node c t1 (a,b) t2) = (case cmp x a of
+"del x (Node t1 (a,b) c t2) = (case cmp x a of
   LT \<Rightarrow> delL x t1 (a,b) t2 |
   GT \<Rightarrow> delR x t1 (a,b) t2 |
   EQ \<Rightarrow> combine t1 t2)" |
 "delL x (B t1 a t2) b t3 = baldL (del x (B t1 a t2)) b t3" |
 "delL x t1 a t2 = R (del x t1) a t2" |