Trees can can be converted
List of Import References : 
See  BOOL 
See  Char 
See  DENOTATION 
See  Nat 
See  Option 
See  Seq 
See  String 
See  Tree 
SIGNATURE TreeConv[data]
$Date: 2010-09-30 18:24:17 +0200 (Do, 30. Sep 2010) $ ($Revision: 616 $)
IMPORT Tree[data] ONLY tree
       Seq[data] ONLY seq
       Seq[seq[data]] ONLY seq
       String ONLY string
SORT data
Trees are represented as follows:
FUN ` : (data -> denotation) -> tree[data] -> denotation FUN ` : (data -> string) -> tree[data] -> string
These functions produce a twodimensional output of the tree. This works only for fixed width fonts, of course. The output assumes arbitrarily long lines. The function aborts, if one representation has zero length.
FUN graphic : (data -> denotation) -> tree[data] -> denotation FUN graphic : (data -> string ) -> tree[data] -> string
There are three possibilities: you can get the datas either in inorder -- left/node/right, in preorder -- node/left/right, or in postorder -- left/right/node.
FUN asSeqIn asSeqPre asSeqPost : tree[data] -> seq[data]
asSeqBreadth gives you a sequence of sequence of
datas. The ith element of the sequence contains all elements of level
i from left to right. 
FUN asSeqBreadth : tree[data] -> seq[seq[data]]
next node: IndexingOfTrees,
 prev node: TreeZip,
 up to node: Subsystem Binary Trees