record TreeMethods {n m : Level } {a : Set n } {t : Set m } (treeImpl : Set n ) : Set (m Level.⊔ n) where
  field
    putImpl : treeImpl -> a -> (treeImpl -> t) -> t
  getImpl  : treeImpl -> (treeImpl -> Maybe a -> t) -> t

record Tree  {n m : Level } {a : Set n } {t : Set m } (treeImpl : Set n ) : Set (m Level.⊔ n) where
  field
    tree : treeImpl
    treeMethods : TreeMethods {n} {m} {a} {t} treeImpl
  putTree : a -> (Tree treeImpl -> t) -> t
  putTree d next = putImpl (treeMethods ) tree d (\t1 -> next (record {tree = t1 ; treeMethods = treeMethods} ))
  getTree : (Tree treeImpl -> Maybe a -> t) -> t
  getTree next = getImpl (treeMethods ) tree (\t1 d -> next (record {tree = t1 ; treeMethods = treeMethods} ) d )