(
  ( tree
  =   1
    .   (2.(4.7.) (5.))
        (3.6.(8.) (9.))
  )
& ( preorder
  =   K sub
    .     !arg:(?K.?sub) ?arg
        & !K preorder$!sub preorder$!arg
      |
  )
& out$("preorder:   " preorder$!tree)
& ( inorder
  =   K lhs rhs
    .   !arg:(?K.?sub) ?arg
      & (   !sub:%?lhs ?rhs
          & inorder$!lhs !K inorder$!rhs inorder$!arg
        | !K
        )
  )
& out$("inorder:    " inorder$!tree)
& ( postorder
  =   K sub
    .     !arg:(?K.?sub) ?arg
        & postorder$!sub !K postorder$!arg
      |
  )
& out$("postorder:  " postorder$!tree)
& ( levelorder
  =   todo tree sub
    .   !arg:(.)&
      |   !arg:(?tree.?todo)
        & (   !tree:(?K.?sub) ?tree
            & !K levelorder$(!tree.!todo !sub)
          | levelorder$(!todo.)
          )
  )
& out$("level-order:" levelorder$(!tree.))
&
)