diff --git a/extra/trees/avl/avl.factor b/extra/trees/avl/avl.factor
index c37448fc1f..264db53a9e 100755
--- a/extra/trees/avl/avl.factor
+++ b/extra/trees/avl/avl.factor
@@ -1,8 +1,8 @@
 ! Copyright (C) 2007 Alex Chapman
 ! See http://factorcode.org/license.txt for BSD license.
 USING: combinators kernel generic math math.functions
-math.parser namespaces io prettyprint.backend sequences trees
-assocs parser accessors math.order ;
+math.parser namespaces io sequences trees
+assocs parser accessors math.order prettyprint.custom ;
 IN: trees.avl
 
 TUPLE: avl < tree ;
@@ -155,4 +155,4 @@ M: avl assoc-like
 : AVL{
     \ } [ >avl ] parse-literal ; parsing
 
-! M: avl pprint-delims drop \ AVL{ \ } ;
+M: avl pprint-delims drop \ AVL{ \ } ;
diff --git a/extra/trees/splay/splay.factor b/extra/trees/splay/splay.factor
index adcf0a2522..c47b6b5d07 100755
--- a/extra/trees/splay/splay.factor
+++ b/extra/trees/splay/splay.factor
@@ -1,7 +1,7 @@
 ! Copyright (c) 2005 Mackenzie Straight.
 ! See http://factorcode.org/license.txt for BSD license.
 USING: arrays kernel math namespaces sequences assocs parser
-prettyprint.backend trees generic math.order accessors ;
+trees generic math.order accessors prettyprint.custom ;
 IN: trees.splay
 
 TUPLE: splay < tree ;
@@ -137,4 +137,4 @@ M: splay new-assoc
 M: splay assoc-like
     drop dup splay? [ >splay ] unless ;
 
-! M: splay pprint-delims drop \ SPLAY{ \ } ;
+M: splay pprint-delims drop \ SPLAY{ \ } ;
diff --git a/extra/trees/trees.factor b/extra/trees/trees.factor
index 892b3b3944..41a8a21c1d 100755
--- a/extra/trees/trees.factor
+++ b/extra/trees/trees.factor
@@ -2,8 +2,7 @@
 ! See http://factorcode.org/license.txt for BSD license.
 USING: kernel generic math sequences arrays io namespaces
 prettyprint.private kernel.private assocs random combinators
-parser prettyprint.backend math.order accessors deques make
-prettyprint.custom ;
+parser math.order accessors deques make prettyprint.custom ;
 IN: trees
 
 TUPLE: tree root count ;
@@ -21,15 +20,17 @@ INSTANCE: tree assoc
 TUPLE: node key value left right ;
 
 : new-node ( key value class -- node )
-    new swap >>value swap >>key ;
+    new
+        swap >>value
+        swap >>key ;
 
 : <node> ( key value -- node )
     node new-node ;
 
 SYMBOL: current-side
 
-: left ( -- symbol ) -1 ; inline
-: right ( -- symbol ) 1 ; inline
+CONSTANT: left -1
+CONSTANT: right 1
 
 : key-side ( k1 k2 -- n )
     <=> {
@@ -46,24 +47,33 @@ SYMBOL: current-side
 
 : node-link@ ( node ? -- node )
     go-left? xor [ left>> ] [ right>> ] if ;
+
 : set-node-link@ ( left parent ? -- ) 
     go-left? xor [ (>>left) ] [ (>>right) ] if ;
 
 : node-link ( node -- child ) f node-link@  ;
+
 : set-node-link ( child node -- ) f set-node-link@ ;
+
 : node+link ( node -- child ) t node-link@ ;
+
 : set-node+link ( child node -- ) t set-node-link@ ;
 
-: with-side ( side quot -- ) [ swap current-side set call ] with-scope ; inline
+: with-side ( side quot -- )
+    [ swap current-side set call ] with-scope ; inline
+
 : with-other-side ( quot -- )
     current-side get neg swap with-side ; inline
+
 : go-left ( quot -- ) left swap with-side ; inline
+
 : go-right ( quot -- ) right swap with-side ; inline
 
 : leaf? ( node -- ? )
     [ left>> ] [ right>> ] bi or not ;
 
-: random-side ( -- side ) left right 2array random ;
+: random-side ( -- side )
+    left right 2array random ;
 
 : choose-branch ( key node -- key node-left/right )
     2dup key>> key-side [ node-link ] with-side ;
@@ -192,6 +202,6 @@ M: tree assoc-like drop dup tree? [ >tree ] unless ;
     \ } [ >tree ] parse-literal ; parsing
                                                         
 M: tree assoc-size count>> ;
-! M: tree pprint-delims drop \ TREE{ \ } ;
-! M: tree >pprint-sequence >alist ;
-! M: tree pprint-narrow? drop t ;
+M: tree pprint-delims drop \ TREE{ \ } ;
+M: tree >pprint-sequence >alist ;
+M: tree pprint-narrow? drop t ;