ABS: Tree(E)

STM: tree wf

STM: tree subtype

STM: tree subtype2

DIR: node object directory

STM: tree leaf wf2

STM: comb for tree leaf wf2

STM: tree node wf2

STM: node wf

STM: comb for node wf

ABS: t_iterate(l;n;t)

STM: t iterate wf

ABS: is_leaf(t)

STM: is leaf wf

ABS: is_node(t)

STM: is node wf

ABS: left_child(t)

STM: left child wf

ABS: right_child(t)

STM: right child wf

ABS: leaf_value(t)

STM: leaf value wf

STM: tree leaf one one

STM: comb for tree leaf wf