diff --git a/nested/src/char_editor.rs b/nested/src/char_editor.rs
index 225c640..bb63295 100644
--- a/nested/src/char_editor.rs
+++ b/nested/src/char_editor.rs
@@ -8,8 +8,9 @@ use {
             TerminalAtom, TerminalEditor, TerminalEditorResult, TerminalEvent, TerminalStyle,
             TerminalView,
         },
-        tree_nav::{TerminalTreeEditor, TreeCursor, TreeNav, TreeNavResult},
-        diagnostics::Diagnostics
+        tree::{TreeCursor, TreeNav, TreeNavResult},
+        diagnostics::Diagnostics,
+        Nested
     },
     std::sync::Arc,
     std::sync::RwLock,
@@ -69,6 +70,6 @@ impl TerminalEditor for CharEditor {
     }
 }
 
-impl TerminalTreeEditor for CharEditor {}
+impl Nested for CharEditor {}
 
 
diff --git a/nested/src/core/context.rs b/nested/src/core/context.rs
index a783512..ec82346 100644
--- a/nested/src/core/context.rs
+++ b/nested/src/core/context.rs
@@ -4,9 +4,7 @@ use {
             type_term::{TypeDict, TypeTerm, TypeID},
             AnyOuterViewPort, OuterViewPort, View,
         },
-        tree_nav::{
-            TerminalTreeEditor
-        }
+        Nested
     },
     std::{
         collections::HashMap,
@@ -244,7 +242,7 @@ pub struct Context {
     objects: HashMap<String, Object>,
 
     /// editors
-    editor_ctors: HashMap<TypeID, Box<dyn Fn(&Self, TypeTerm) -> Option<Arc<RwLock<dyn TerminalTreeEditor>>> + Send + Sync>>,
+    editor_ctors: HashMap<TypeID, Box<dyn Fn(&Self, TypeTerm) -> Option<Arc<RwLock<dyn Nested>>> + Send + Sync>>,
 
     /// morphisms
     default_constructors: HashMap<TypeTerm, Box<dyn Fn() -> Object + Send + Sync>>,
@@ -281,7 +279,7 @@ impl Context {
         self.type_dict.type_term_to_str(&t)
     }
 
-    pub fn add_editor_ctor(&mut self, tn: &str, mk_editor: Box<dyn Fn(&Self, TypeTerm) -> Option<Arc<RwLock<dyn TerminalTreeEditor>>> + Send + Sync>) {
+    pub fn add_editor_ctor(&mut self, tn: &str, mk_editor: Box<dyn Fn(&Self, TypeTerm) -> Option<Arc<RwLock<dyn Nested>>> + Send + Sync>) {
         if let Some(tid) = self.type_dict.get_typeid(&tn.into()) {
             self.editor_ctors.insert(tid, mk_editor);
         } else {
@@ -289,7 +287,7 @@ impl Context {
         }
     }
 
-    pub fn make_editor(&self, type_term: TypeTerm) -> Option<Arc<RwLock<dyn TerminalTreeEditor>>> {
+    pub fn make_editor(&self, type_term: TypeTerm) -> Option<Arc<RwLock<dyn Nested>>> {
         if let TypeTerm::Type{ id, args } = type_term.clone() {
             let mk_editor = self.editor_ctors.get(&id)?;
             mk_editor(self, type_term)
@@ -297,7 +295,7 @@ impl Context {
             None
         }
     }
-    
+
     pub fn add_morphism(
         &mut self,
         morph_type: MorphismType,
diff --git a/nested/src/core/port.rs b/nested/src/core/port.rs
index 0cba29d..b20ec50 100644
--- a/nested/src/core/port.rs
+++ b/nested/src/core/port.rs
@@ -330,3 +330,4 @@ where
 }
 
 //<<<<>>>><<>><><<>><<<*>>><<>><><<>><<<<>>>>
+
diff --git a/nested/src/integer/editor.rs b/nested/src/integer/editor.rs
index d4dd244..003b845 100644
--- a/nested/src/integer/editor.rs
+++ b/nested/src/integer/editor.rs
@@ -10,8 +10,9 @@ use {
             TerminalAtom, TerminalEditor, TerminalEditorResult, TerminalEvent, TerminalStyle,
             TerminalView, make_label
         },
-        tree_nav::{TerminalTreeEditor, TreeCursor, TreeNav, TreeNavResult},
-        diagnostics::{Diagnostics, Message}
+        tree::{TreeCursor, TreeNav, TreeNavResult},
+        diagnostics::{Diagnostics, Message},
+        Nested
     },
     std::sync::Arc,
     std::sync::RwLock,
@@ -95,7 +96,7 @@ impl TerminalEditor for DigitEditor {
     }
 }
 
-impl TerminalTreeEditor for DigitEditor {}
+impl Nested for DigitEditor {}
 
 impl Diagnostics for DigitEditor {
     fn get_msg_port(&self) -> OuterViewPort<dyn SequenceView<Item = crate::diagnostics::Message>> {
@@ -205,5 +206,5 @@ impl TerminalEditor for PosIntEditor {
     }
 }
 
-impl TerminalTreeEditor for PosIntEditor {}
+impl Nested for PosIntEditor {}
 
diff --git a/nested/src/lib.rs b/nested/src/lib.rs
index 83d3384..842e9d6 100644
--- a/nested/src/lib.rs
+++ b/nested/src/lib.rs
@@ -20,7 +20,7 @@ pub mod vec;
 pub mod product;
 pub mod sum;
 pub mod list;
-pub mod tree_nav;
+pub mod tree;
 pub mod diagnostics;
 
 // high-level types
@@ -35,3 +35,16 @@ pub mod terminal;
 pub fn magic_header() {
     eprintln!("<<<<>>>><<>><><<>><<<*>>><<>><><<>><<<<>>>>");
 }
+
+use crate::terminal::{TerminalEditor};
+use crate::diagnostics::{Diagnostics};
+use crate::tree::{TreeNav, TreeType};
+
+pub trait Nested
+    : TerminalEditor
+    + TreeNav
+//   + TreeType
+    + Diagnostics
+    + Send
+{}
+
diff --git a/nested/src/list/editor.rs b/nested/src/list/editor.rs
index 78d9c94..799116e 100644
--- a/nested/src/list/editor.rs
+++ b/nested/src/list/editor.rs
@@ -12,7 +12,8 @@ use {
             make_label, TerminalEditor, TerminalEditorResult, TerminalEvent, TerminalStyle,
             TerminalView,
         },
-        tree_nav::{TerminalTreeEditor, TreeCursor, TreeNav, TreeNavResult},
+        Nested,
+        tree::{TreeCursor, TreeNav, TreeNavResult},
         vec::VecBuffer,
         color::{bg_style_from_depth, fg_style_from_depth}
     },
@@ -23,7 +24,7 @@ use {
 //<<<<>>>><<>><><<>><<<*>>><<>><><<>><<<<>>>>
                                                             
 pub struct ListEditor<ItemEditor>
-where ItemEditor: TerminalTreeEditor + ?Sized + Send + Sync + 'static
+where ItemEditor: Nested + ?Sized + Send + Sync + 'static
 {
     pub(super) cursor: SingletonBuffer<ListCursor>,
     pub(super) data: VecBuffer<Arc<RwLock<ItemEditor>>>,
@@ -34,7 +35,7 @@ where ItemEditor: TerminalTreeEditor + ?Sized + Send + Sync + 'static
 }
 
 impl<ItemEditor> ListEditor<ItemEditor>
-where ItemEditor: TerminalTreeEditor + ?Sized + Send + Sync + 'static
+where ItemEditor: Nested + ?Sized + Send + Sync + 'static
 {
     pub fn new(make_item_editor: impl Fn() -> Arc<RwLock<ItemEditor>> + Send + Sync + 'static, depth: usize) -> Self {
         ListEditor {
@@ -58,7 +59,7 @@ where ItemEditor: TerminalTreeEditor + ?Sized + Send + Sync + 'static
         );
         segment_view_port.into_outer().map(move |segment| segment.pty_view())
     }
-    
+
     pub fn get_data_port(&self) -> OuterViewPort<dyn SequenceView<Item = Arc<RwLock<ItemEditor>>>> {
         self.data.get_port().to_sequence()
     }
diff --git a/nested/src/list/nav.rs b/nested/src/list/nav.rs
index 9728d2f..bcc9c8b 100644
--- a/nested/src/list/nav.rs
+++ b/nested/src/list/nav.rs
@@ -12,9 +12,10 @@ use {
             make_label, TerminalEditor, TerminalEditorResult, TerminalEvent, TerminalStyle,
             TerminalView,
         },
-        tree_nav::{TerminalTreeEditor, TreeCursor, TreeNav, TreeNavResult},
+        tree::{TreeCursor, TreeNav, TreeNavResult},
         vec::VecBuffer,
-        color::{bg_style_from_depth, fg_style_from_depth}
+        color::{bg_style_from_depth, fg_style_from_depth},
+        Nested
     },
     std::sync::{Arc, RwLock},
     termion::event::{Event, Key},
@@ -22,7 +23,7 @@ use {
 };
 
 impl<ItemEditor> TreeNav for ListEditor<ItemEditor>
-where ItemEditor: TerminalTreeEditor + ?Sized + Send + Sync + 'static
+where ItemEditor: Nested + ?Sized + Send + Sync + 'static
 {
     fn get_cursor_warp(&self) -> TreeCursor {
         let cur = self.cursor.get();
diff --git a/nested/src/list/pty_editor.rs b/nested/src/list/pty_editor.rs
index 8f402fc..8235b36 100644
--- a/nested/src/list/pty_editor.rs
+++ b/nested/src/list/pty_editor.rs
@@ -12,10 +12,11 @@ use {
             make_label, TerminalEditor, TerminalEditorResult, TerminalEvent, TerminalStyle,
             TerminalView,
         },
-        tree_nav::{TerminalTreeEditor, TreeCursor, TreeNav, TreeNavResult},
+        tree::{TreeCursor, TreeNav, TreeNavResult},
         diagnostics::{Diagnostics},
         vec::VecBuffer,
-        color::{bg_style_from_depth, fg_style_from_depth}
+        color::{bg_style_from_depth, fg_style_from_depth},
+        Nested
     },
     std::sync::{Arc, RwLock},
     termion::event::{Event, Key},
@@ -23,7 +24,7 @@ use {
 };
 
 pub struct PTYListEditor<ItemEditor>
-where ItemEditor: TerminalTreeEditor + ?Sized + Send + Sync + 'static
+where ItemEditor: Nested + ?Sized + Send + Sync + 'static
 {
     pub editor: ListEditor<ItemEditor>,
 
@@ -36,7 +37,7 @@ where ItemEditor: TerminalTreeEditor + ?Sized + Send + Sync + 'static
 }
 
 impl<ItemEditor> PTYListEditor<ItemEditor>
-where ItemEditor: TerminalTreeEditor + ?Sized + Send + Sync + 'static
+where ItemEditor: Nested + ?Sized + Send + Sync + 'static
 {
     pub fn new(
         make_item_editor: impl Fn() -> Arc<RwLock<ItemEditor>> + Send + Sync + 'static,
@@ -92,7 +93,7 @@ where ItemEditor: TerminalTreeEditor + ?Sized + Send + Sync + 'static
 }
 
 impl<ItemEditor> TerminalEditor for PTYListEditor<ItemEditor>
-where ItemEditor: TerminalTreeEditor + ?Sized + Send + Sync + 'static
+where ItemEditor: Nested + ?Sized + Send + Sync + 'static
 {
     fn get_term_view(&self) -> OuterViewPort<dyn TerminalView> {
         self.editor
@@ -229,7 +230,7 @@ where ItemEditor: TerminalTreeEditor + ?Sized + Send + Sync + 'static
 }
 
 impl<ItemEditor> TreeNav for PTYListEditor<ItemEditor>
-where ItemEditor: TerminalTreeEditor + ?Sized + Send + Sync + 'static
+where ItemEditor: Nested + ?Sized + Send + Sync + 'static
 {
     fn get_cursor_warp(&self) -> TreeCursor {
         self.editor.get_cursor_warp()
@@ -249,7 +250,7 @@ where ItemEditor: TerminalTreeEditor + ?Sized + Send + Sync + 'static
 }
 
 impl<ItemEditor> Diagnostics for PTYListEditor<ItemEditor>
-where ItemEditor: TerminalTreeEditor + Diagnostics + ?Sized + Send + Sync + 'static
+where ItemEditor: Nested + Diagnostics + ?Sized + Send + Sync + 'static
 {
     fn get_msg_port(&self) -> OuterViewPort<dyn SequenceView<Item = crate::diagnostics::Message>> {
         self.editor
@@ -273,8 +274,8 @@ where ItemEditor: TerminalTreeEditor + Diagnostics + ?Sized + Send + Sync + 'sta
     }
 }
 
-impl<ItemEditor> TerminalTreeEditor for PTYListEditor<ItemEditor>
-where ItemEditor: TerminalTreeEditor + ?Sized + Send + Sync + 'static
+impl<ItemEditor> Nested for PTYListEditor<ItemEditor>
+where ItemEditor: Nested + ?Sized + Send + Sync + 'static
 {}
 
 use crate::{
diff --git a/nested/src/list/segment.rs b/nested/src/list/segment.rs
index 6e125e8..0aa2819 100644
--- a/nested/src/list/segment.rs
+++ b/nested/src/list/segment.rs
@@ -6,7 +6,7 @@ use {
         sequence::SequenceView,
         singleton::SingletonView,
         terminal::{TerminalView, TerminalStyle, make_label},
-        tree_nav::TerminalTreeEditor,
+        Nested,
         color::{bg_style_from_depth, fg_style_from_depth}
     },
     std::sync::Arc,
@@ -14,7 +14,7 @@ use {
 };
 
 pub enum ListSegment<ItemEditor>
-where ItemEditor: TerminalTreeEditor + ?Sized + Send + Sync + 'static
+where ItemEditor: Nested + ?Sized + Send + Sync + 'static
 {
     InsertCursor,
     Item {
@@ -29,7 +29,7 @@ pub trait PTYSegment {
 }
 
 impl<ItemEditor> PTYSegment for ListSegment<ItemEditor>
-where ItemEditor: TerminalTreeEditor + ?Sized + Send + Sync + 'static
+where ItemEditor: Nested + ?Sized + Send + Sync + 'static
 {
     fn pty_view(&self) -> OuterViewPort<dyn TerminalView> {
         match self {
@@ -64,7 +64,7 @@ where ItemEditor: TerminalTreeEditor + ?Sized + Send + Sync + 'static
 }
 
 pub struct ListSegmentSequence<ItemEditor>
-where ItemEditor: TerminalTreeEditor + ?Sized + Send + Sync + 'static
+where ItemEditor: Nested + ?Sized + Send + Sync + 'static
 {
     data: Arc<dyn SequenceView<Item = Arc<RwLock<ItemEditor>>>>,
     cursor: Arc<dyn SingletonView<Item = ListCursor>>,
@@ -77,13 +77,13 @@ where ItemEditor: TerminalTreeEditor + ?Sized + Send + Sync + 'static
 }
 
 impl<ItemEditor> View for ListSegmentSequence<ItemEditor>
-where ItemEditor: TerminalTreeEditor + ?Sized + Send + Sync + 'static
+where ItemEditor: Nested + ?Sized + Send + Sync + 'static
 {
     type Msg = usize;
 }
 
 impl<ItemEditor> SequenceView for ListSegmentSequence<ItemEditor>
-where ItemEditor: TerminalTreeEditor + ?Sized + Send + Sync + 'static
+where ItemEditor: Nested + ?Sized + Send + Sync + 'static
 {
     type Item = ListSegment<ItemEditor>;
 
@@ -136,7 +136,7 @@ where ItemEditor: TerminalTreeEditor + ?Sized + Send + Sync + 'static
 }
 
 impl<ItemEditor> ListSegmentSequence<ItemEditor>
-where ItemEditor: TerminalTreeEditor + ?Sized + Send + Sync + 'static
+where ItemEditor: Nested + ?Sized + Send + Sync + 'static
 {
     pub fn new(
         cursor_port: OuterViewPort<dyn SingletonView<Item = ListCursor>>,
diff --git a/nested/src/make_editor.rs b/nested/src/make_editor.rs
index 929b7d8..7f3e4ce 100644
--- a/nested/src/make_editor.rs
+++ b/nested/src/make_editor.rs
@@ -1,26 +1,60 @@
 
 use {
     crate::{
-        core::{TypeLadder, Context},
-        terminal::{TerminalView},
-        tree_nav::{TerminalTreeEditor},
+        core::{TypeLadder, Context, OuterViewPort},
+        terminal::{TerminalView, TerminalEditor, TerminalEvent, TerminalEditorResult, make_label},
+        tree::{TreeNav},
         integer::PosIntEditor,
         list::{ListEditor, PTYListEditor},
         sequence::{decorator::{SeqDecorStyle}},
         product::editor::ProductEditor,
-        char_editor::CharEditor
+        char_editor::CharEditor,
+        diagnostics::Diagnostics,
+        Nested
     },
     cgmath::{Vector2, Point2},
     std::sync::{Arc, RwLock},
 };
 
-pub fn make_editor(ctx: Arc<RwLock<Context>>, t: &TypeLadder, depth: usize) -> Arc<RwLock<dyn TerminalTreeEditor + Send + Sync>> {
+enum RhsNode {
+    Sum (
+        Arc<RwLock< PTYListEditor< RhsNode > >>
+    ),
+    Product (
+        Arc<RwLock< PTYListEditor< RhsNode > >>
+    ),
+    String(
+        Arc<RwLock< PTYListEditor< CharEditor > >>
+    )
+}
+
+impl TreeNav for RhsNode {}
+
+impl TerminalEditor for RhsNode {
+    fn get_term_view(&self) -> OuterViewPort<dyn TerminalView> {
+        make_label("todo")
+    }
+
+    fn handle_terminal_event(&mut self, event: &TerminalEvent) -> TerminalEditorResult {
+        TerminalEditorResult::Continue
+    }
+}
+
+impl Diagnostics for RhsNode {}
+impl Nested for RhsNode {}
+
+struct GrammarRuleEditor {
+    lhs: Arc<RwLock<PTYListEditor<CharEditor>>>,
+    rhs: Arc<RwLock<PTYListEditor<RhsNode>>>
+}
+
+pub fn make_editor(ctx: Arc<RwLock<Context>>, t: &TypeLadder, depth: usize) -> Arc<RwLock<dyn Nested + Send + Sync>> {
     let c = ctx.read().unwrap();
     if t[0] == c.type_term_from_str("( PosInt 16 BigEndian )").unwrap() {
-        Arc::new(RwLock::new(PosIntEditor::new(16))) as Arc<RwLock<dyn TerminalTreeEditor + Send + Sync>>
+        Arc::new(RwLock::new(PosIntEditor::new(16))) as Arc<RwLock<dyn Nested + Send + Sync>>
 
     } else if t[0] == c.type_term_from_str("( PosInt 10 BigEndian )").unwrap() {
-        Arc::new(RwLock::new(PosIntEditor::new(10))) as Arc<RwLock<dyn TerminalTreeEditor + Send + Sync>>
+        Arc::new(RwLock::new(PosIntEditor::new(10))) as Arc<RwLock<dyn Nested + Send + Sync>>
 
     } else if t[0] == c.type_term_from_str("( String )").unwrap() {
         Arc::new(RwLock::new(
@@ -64,7 +98,7 @@ pub fn make_editor(ctx: Arc<RwLock<Context>>, t: &TypeLadder, depth: usize) -> A
                 '"',
                 depth
             )
-        )) as Arc<RwLock<dyn TerminalTreeEditor + Send + Sync>>
+        )) as Arc<RwLock<dyn Nested + Send + Sync>>
     } else if t[0] == c.type_term_from_str("( List Symbol )").unwrap() {
         Arc::new(RwLock::new(
             PTYListEditor::new(
@@ -83,7 +117,7 @@ pub fn make_editor(ctx: Arc<RwLock<Context>>, t: &TypeLadder, depth: usize) -> A
                 ' ',
                 depth
             )
-        )) as Arc<RwLock<dyn TerminalTreeEditor + Send + Sync>>
+        )) as Arc<RwLock<dyn Nested + Send + Sync>>
 
     } else if t[0] == c.type_term_from_str("( List Char )").unwrap() {
         Arc::new(RwLock::new(
@@ -95,7 +129,7 @@ pub fn make_editor(ctx: Arc<RwLock<Context>>, t: &TypeLadder, depth: usize) -> A
                 '\n',
                 depth+1
             )
-        )) as Arc<RwLock<dyn TerminalTreeEditor + Send + Sync>>
+        )) as Arc<RwLock<dyn Nested + Send + Sync>>
 
     } else if t[0] == c.type_term_from_str("( List ℕ )").unwrap() {
         Arc::new(RwLock::new(
@@ -107,7 +141,7 @@ pub fn make_editor(ctx: Arc<RwLock<Context>>, t: &TypeLadder, depth: usize) -> A
                 ',',
                 depth
             )
-        )) as Arc<RwLock<dyn TerminalTreeEditor + Send + Sync>>
+        )) as Arc<RwLock<dyn Nested + Send + Sync>>
 
     } else if t[0] == c.type_term_from_str("( Path )").unwrap() {
         Arc::new(RwLock::new(PTYListEditor::new(
@@ -126,7 +160,7 @@ pub fn make_editor(ctx: Arc<RwLock<Context>>, t: &TypeLadder, depth: usize) -> A
             SeqDecorStyle::Path,
             '/',
             depth
-        ))) as Arc<RwLock<dyn TerminalTreeEditor + Send + Sync>>
+        ))) as Arc<RwLock<dyn Nested + Send + Sync>>
 
     } else if t[0] == c.type_term_from_str("( List Path )").unwrap() {
         Arc::new(RwLock::new(
@@ -146,11 +180,11 @@ pub fn make_editor(ctx: Arc<RwLock<Context>>, t: &TypeLadder, depth: usize) -> A
                 ',',
                 depth
             )
-        )) as Arc<RwLock<dyn TerminalTreeEditor + Send + Sync>>
+        )) as Arc<RwLock<dyn Nested + Send + Sync>>
 
     } else if t[0] == c.type_term_from_str("( List RGB )").unwrap() {
         Arc::new(RwLock::new(
-            PTYListEditor::<dyn TerminalTreeEditor + Send +Sync>::new(
+            PTYListEditor::<dyn Nested + Send +Sync>::new(
                 {
                     let d = depth+1;
                     let ctx = ctx.clone();
@@ -162,7 +196,7 @@ pub fn make_editor(ctx: Arc<RwLock<Context>>, t: &TypeLadder, depth: usize) -> A
                 ',',
                 depth
             )
-        )) as Arc<RwLock<dyn TerminalTreeEditor + Send + Sync>>
+        )) as Arc<RwLock<dyn Nested + Send + Sync>>
 
     } else if t[0] == c.type_term_from_str("( RGB )").unwrap() {
         Arc::new(RwLock::new(ProductEditor::new(depth, ctx.clone())
@@ -174,7 +208,7 @@ pub fn make_editor(ctx: Arc<RwLock<Context>>, t: &TypeLadder, depth: usize) -> A
                              .with_t(Point2::new(1, 3), "b: ")
                              .with_n(Point2::new(2, 3), vec![ ctx.read().unwrap().type_term_from_str("( PosInt 16 BigEndian )").unwrap() ] )
                              .with_t(Point2::new(0, 4), "}   ")
-        )) as Arc<RwLock<dyn TerminalTreeEditor + Send + Sync>>
+        )) as Arc<RwLock<dyn Nested + Send + Sync>>
 
     } else if t[0] == c.type_term_from_str("( Vec3i )").unwrap() {
         Arc::new(RwLock::new(ProductEditor::new(depth, ctx.clone())
@@ -186,11 +220,11 @@ pub fn make_editor(ctx: Arc<RwLock<Context>>, t: &TypeLadder, depth: usize) -> A
                              .with_t(Point2::new(1, 3), "z: ")
                              .with_n(Point2::new(2, 3), vec![ ctx.read().unwrap().type_term_from_str("( PosInt 10 BigEndian )").unwrap() ] )
                              .with_t(Point2::new(0, 4), "}")
-        )) as Arc<RwLock<dyn TerminalTreeEditor + Send + Sync>>
+        )) as Arc<RwLock<dyn Nested + Send + Sync>>
 
     } else if t[0] == c.type_term_from_str("( Json )").unwrap() {
         Arc::new(RwLock::new(
-            PTYListEditor::<dyn TerminalTreeEditor + Send + Sync>::new(
+            PTYListEditor::<dyn Nested + Send + Sync>::new(
                 Box::new({
                     let ctx = ctx.clone();
                     move || {
@@ -198,18 +232,18 @@ pub fn make_editor(ctx: Arc<RwLock<Context>>, t: &TypeLadder, depth: usize) -> A
                                              .with_n(Point2::new(0, 0), vec![ ctx.read().unwrap().type_term_from_str("( String )").unwrap() ] )
                                              .with_t(Point2::new(1, 0), ": ")
                                              .with_n(Point2::new(2, 0), vec![ ctx.read().unwrap().type_term_from_str("( Json )").unwrap() ] )
-                        )) as Arc<RwLock<dyn TerminalTreeEditor + Send + Sync>>
+                        )) as Arc<RwLock<dyn Nested + Send + Sync>>
                     }
                 }),
                 SeqDecorStyle::VerticalSexpr,
                 '\n',
                 depth
             )
-        )) as Arc<RwLock<dyn TerminalTreeEditor + Send + Sync>>
+        )) as Arc<RwLock<dyn Nested + Send + Sync>>
             
     } else if t[0] == c.type_term_from_str("( List Term )").unwrap() {
         Arc::new(RwLock::new(
-            PTYListEditor::<dyn TerminalTreeEditor + Send + Sync>::new(
+            PTYListEditor::<dyn Nested + Send + Sync>::new(
                 Box::new({
                     let ctx = ctx.clone();
                     move || {
@@ -220,7 +254,7 @@ pub fn make_editor(ctx: Arc<RwLock<Context>>, t: &TypeLadder, depth: usize) -> A
                 '\n',
                 depth
             )
-        )) as Arc<RwLock<dyn TerminalTreeEditor + Send + Sync>>
+        )) as Arc<RwLock<dyn Nested + Send + Sync>>
 
     } else { // else: term
         Arc::new(RwLock::new(
diff --git a/nested/src/product/editor.rs b/nested/src/product/editor.rs
index 3c36be5..4ab8357 100644
--- a/nested/src/product/editor.rs
+++ b/nested/src/product/editor.rs
@@ -12,9 +12,11 @@ use {
         sequence::{SequenceView},
         make_editor::make_editor,
 
-        tree_nav::{TreeNav, TerminalTreeEditor, TreeNavResult},
+        tree::{TreeNav, TreeNavResult},
         diagnostics::{Diagnostics, Message},
-        terminal::{TerminalStyle}
+        terminal::{TerminalStyle},
+
+        Nested
     },
     cgmath::{Vector2, Point2},
     std::sync::{Arc, RwLock},
@@ -111,7 +113,7 @@ impl ProductEditor {
         Some(self.get_editor_segment_mut(self.cursor?))
     }
 
-    pub fn get_editor(&self, idx: isize) -> Option<Arc<RwLock<dyn TerminalTreeEditor + Send + Sync>>> {
+    pub fn get_editor(&self, idx: isize) -> Option<Arc<RwLock<dyn Nested + Send + Sync>>> {
         if let ProductEditorSegment::N{ t: _, editor, ed_depth: _, cur_depth: _, cur_dist: _ } = self.get_editor_segment(idx) {
             editor
         } else {
@@ -119,7 +121,7 @@ impl ProductEditor {
         }
     }
 
-    pub fn get_cur_editor(&self) -> Option<Arc<RwLock<dyn TerminalTreeEditor + Send + Sync>>> {
+    pub fn get_cur_editor(&self) -> Option<Arc<RwLock<dyn Nested + Send + Sync>>> {
         self.get_editor(self.cursor?)
     }
 
diff --git a/nested/src/product/nav.rs b/nested/src/product/nav.rs
index 8ff801f..0a74921 100644
--- a/nested/src/product/nav.rs
+++ b/nested/src/product/nav.rs
@@ -1,9 +1,10 @@
 use {
     crate::{
         list::ListCursorMode,
-        tree_nav::{TreeNav, TreeNavResult, TreeCursor, TerminalTreeEditor},
+        tree::{TreeNav, TreeNavResult, TreeCursor},
         product::{segment::ProductEditorSegment, ProductEditor},
-        make_editor::{make_editor}
+        make_editor::{make_editor},
+        Nested
     },
     cgmath::{Point2, Vector2},
     std::{sync::{Arc, RwLock}, ops::{Deref, DerefMut}},
@@ -248,5 +249,5 @@ impl TreeNav for ProductEditor {
     }
 }
 
-impl TerminalTreeEditor for ProductEditor {}
+impl Nested for ProductEditor {}
 
diff --git a/nested/src/product/segment.rs b/nested/src/product/segment.rs
index 2ceefc6..5ecd717 100644
--- a/nested/src/product/segment.rs
+++ b/nested/src/product/segment.rs
@@ -6,8 +6,8 @@ use {
             make_label
         },
         list::{ListCursorMode},
-        tree_nav::{TerminalTreeEditor},
-        color::{bg_style_from_depth, fg_style_from_depth}
+        color::{bg_style_from_depth, fg_style_from_depth},
+        Nested
     },
     std::{sync::{Arc, RwLock}, ops::{Deref, DerefMut}},
     termion::event::{Event, Key},
@@ -18,7 +18,7 @@ pub enum ProductEditorSegment {
     T( String, usize ),
     N {
         t: TypeLadder,
-        editor: Option<Arc<RwLock<dyn TerminalTreeEditor + Send + Sync>>>,
+        editor: Option<Arc<RwLock<dyn Nested + Send + Sync>>>,
         ed_depth: usize,
         cur_depth: usize,
         cur_dist: isize
diff --git a/nested/src/sum/editor.rs b/nested/src/sum/editor.rs
index bc590dc..d7f4bf1 100644
--- a/nested/src/sum/editor.rs
+++ b/nested/src/sum/editor.rs
@@ -12,9 +12,10 @@ use {
         sequence::{SequenceView},
         make_editor::make_editor,
 
-        tree_nav::{TreeNav, TreeCursor, TerminalTreeEditor, TreeNavResult},
+        tree::{TreeNav, TreeCursor, TreeNavResult},
         diagnostics::{Diagnostics, Message},
-        terminal::{TerminalStyle}
+        terminal::{TerminalStyle},
+        Nested
     },
     cgmath::{Vector2, Point2},
     std::sync::{Arc, RwLock},
@@ -24,7 +25,7 @@ use {
 
 pub struct SumEditor {
     cur: usize,
-    editors: Vec< Arc<RwLock<dyn TerminalTreeEditor + Send + Sync>> >,
+    editors: Vec< Arc<RwLock<dyn Nested + Send + Sync>> >,
 
     port: ViewPort< dyn TerminalView >,
     diag_port: OuterViewPort< dyn SequenceView<Item = Message> >
@@ -32,7 +33,7 @@ pub struct SumEditor {
 
 impl SumEditor {
     pub fn new(
-        editors: Vec< Arc<RwLock<dyn TerminalTreeEditor + Send + Sync>> >
+        editors: Vec< Arc<RwLock<dyn Nested + Send + Sync>> >
     ) -> Self {
         let port = ViewPort::new();
         let mut diag_buf = VecBuffer::new();
@@ -44,11 +45,12 @@ impl SumEditor {
             diag_port: diag_buf.get_port().to_sequence()
         }
     }
-    
+
     pub fn select(&mut self, idx: usize) {
         self.cur = idx;
         let tv = self.editors[ self.cur ].read().unwrap().get_term_view();
         tv.add_observer( self.port.get_cast() );
+        self.port.update_hooks.write().unwrap().clear();
         self.port.add_update_hook( Arc::new(tv.0.clone()) );
         self.port.set_view( Some(tv.get_view_arc()) );
     }
@@ -81,6 +83,9 @@ impl TerminalEditor for SumEditor {
         match event {
             TerminalEvent::Input( termion::event::Event::Key(Key::Ctrl('x')) ) => {
                 self.select( (self.cur + 1) % self.editors.len() );
+                if self.editors[ self.cur ].read().unwrap().get_cursor().tree_addr.len() == 0 {
+                    self.dn();
+                }
                 TerminalEditorResult::Continue
             },
             event => {
@@ -96,6 +101,6 @@ impl Diagnostics for SumEditor {
     }
 }
 
-impl TerminalTreeEditor for SumEditor {}
+impl Nested for SumEditor {}
 
 
diff --git a/nested/src/tree/cursor.rs b/nested/src/tree/cursor.rs
new file mode 100644
index 0000000..4827e96
--- /dev/null
+++ b/nested/src/tree/cursor.rs
@@ -0,0 +1,35 @@
+use {
+    crate::list::ListCursorMode,
+    cgmath::Vector2
+};
+
+//<<<<>>>><<>><><<>><<<*>>><<>><><<>><<<<>>>>
+
+#[derive(Clone, Eq, PartialEq)]
+pub struct TreeCursor {
+    pub leaf_mode: ListCursorMode,
+    pub tree_addr: Vec<isize>,
+}
+
+impl TreeCursor {
+    pub fn home() -> Self {
+        TreeCursor {
+            leaf_mode: ListCursorMode::Insert,
+            tree_addr: vec![0]
+        }
+    }
+
+    pub fn none() -> Self {
+        TreeCursor {
+            leaf_mode: ListCursorMode::Select,
+            tree_addr: vec![],
+        }
+    }
+}
+
+impl Default for TreeCursor {
+    fn default() -> Self {
+        TreeCursor::none()
+    }
+}
+
diff --git a/nested/src/tree/mod.rs b/nested/src/tree/mod.rs
new file mode 100644
index 0000000..d41e2fb
--- /dev/null
+++ b/nested/src/tree/mod.rs
@@ -0,0 +1,18 @@
+pub mod cursor;
+pub mod nav;
+pub mod typeinfo;
+
+pub struct TreeAddr(Vec<usize>);
+
+impl From<Vec<usize>> for TreeAddr {
+    fn from(v: Vec<usize>) -> TreeAddr {
+        TreeAddr(v)
+    }
+}
+
+pub use {
+    cursor::TreeCursor,
+    nav::{TreeNav, TreeNavResult},
+    typeinfo::TreeType
+};
+
diff --git a/nested/src/tree_nav.rs b/nested/src/tree/nav.rs
similarity index 81%
rename from nested/src/tree_nav.rs
rename to nested/src/tree/nav.rs
index 0c18c6a..c2f23cc 100644
--- a/nested/src/tree_nav.rs
+++ b/nested/src/tree/nav.rs
@@ -1,5 +1,6 @@
 use {
     crate::list::ListCursorMode,
+    crate::tree::TreeCursor,
     cgmath::Vector2
 };
 
@@ -20,34 +21,6 @@ impl From<TreeNavResult> for TerminalEditorResult {
 }
  */
 
-#[derive(Clone, Eq, PartialEq)]
-pub struct TreeCursor {
-    pub leaf_mode: ListCursorMode,
-    pub tree_addr: Vec<isize>,
-}
-
-impl TreeCursor {
-    pub fn home() -> Self {
-        TreeCursor {
-            leaf_mode: ListCursorMode::Insert,
-            tree_addr: vec![0]
-        }
-    }
-
-    pub fn none() -> Self {
-        TreeCursor {
-            leaf_mode: ListCursorMode::Select,
-            tree_addr: vec![],
-        }
-    }
-}
-
-impl Default for TreeCursor {
-    fn default() -> Self {
-        TreeCursor::none()
-    }
-}
-
 pub trait TreeNav {
     /* CORE
     */
@@ -59,6 +32,10 @@ pub trait TreeNav {
         TreeCursor::default()
     }
 
+    fn get_max_depth(&self) -> usize {
+        0
+    }
+
     fn goby(&mut self, direction: Vector2<isize>) -> TreeNavResult {
         TreeNavResult::Exit
     }
@@ -149,8 +126,3 @@ pub trait TreeNav {
     }
 }
 
-use crate::terminal::{TerminalEditor};
-use crate::diagnostics::{Diagnostics};
-
-pub trait TerminalTreeEditor : TerminalEditor + TreeNav + Diagnostics + Send {}
-
diff --git a/shell/src/command.rs b/shell/src/command.rs
index 2076770..91a8717 100644
--- a/shell/src/command.rs
+++ b/shell/src/command.rs
@@ -16,30 +16,32 @@ use {
         terminal::{
             TerminalAtom, TerminalEditor, TerminalEditorResult, TerminalEvent, TerminalStyle, TerminalView, make_label
         },
-        tree_nav::{TreeCursor, TreeNav, TreeNavResult, TerminalTreeEditor},
+        tree::{TreeCursor, TreeNav, TreeNavResult},
         diagnostics::{Diagnostics},
         make_editor::make_editor,
-        product::ProductEditor
+        product::ProductEditor,
+        sum::SumEditor,
+        Nested
     }
 };
 
 trait Action {
-    fn make_editor(&self, ctx: Arc<RwLock<Context>>) -> Arc<RwLock<dyn TerminalTreeEditor + Send + Sync>>;
+    fn make_editor(&self, ctx: Arc<RwLock<Context>>) -> Arc<RwLock<dyn Nested + Send + Sync>>;
 }
 
 pub struct ActCd {}
 impl Action for ActCd {
-    fn make_editor(&self, ctx: Arc<RwLock<Context>>) -> Arc<RwLock<dyn TerminalTreeEditor + Send + Sync>> {
+    fn make_editor(&self, ctx: Arc<RwLock<Context>>) -> Arc<RwLock<dyn Nested + Send + Sync>> {
         let depth = 1;
         Arc::new(RwLock::new(ProductEditor::new(depth, ctx.clone())
                              .with_n(Point2::new(0, 0), vec![ ctx.read().unwrap().type_term_from_str("( Path )").unwrap() ] )
-        )) as Arc<RwLock<dyn TerminalTreeEditor + Send + Sync>>
+        )) as Arc<RwLock<dyn Nested + Send + Sync>>
     }
 }
 
 pub struct ActLs {}
 impl Action for ActLs {
-    fn make_editor(&self, ctx: Arc<RwLock<Context>>) -> Arc<RwLock<dyn TerminalTreeEditor + Send + Sync>> {
+    fn make_editor(&self, ctx: Arc<RwLock<Context>>) -> Arc<RwLock<dyn Nested + Send + Sync>> {
         let depth = 1;
         Arc::new(RwLock::new(ProductEditor::new(depth, ctx.clone())
                              .with_t(Point2::new(1, 0), " Files")
@@ -47,24 +49,39 @@ impl Action for ActLs {
                              .with_t(Point2::new(1, 1), " Options")
                              .with_n(Point2::new(0, 1), vec![ ctx.read().unwrap().type_term_from_str("( List String )").unwrap() ] )
 
-        )) as Arc<RwLock<dyn TerminalTreeEditor + Send + Sync>>
+        )) as Arc<RwLock<dyn Nested + Send + Sync>>
     }
 }
 
 pub struct ActEcho {}
 impl Action for ActEcho {
-    fn make_editor(&self, ctx: Arc<RwLock<Context>>) -> Arc<RwLock<dyn TerminalTreeEditor + Send + Sync>> {
+    fn make_editor(&self, ctx: Arc<RwLock<Context>>) -> Arc<RwLock<dyn Nested + Send + Sync>> {
         let depth = 1;
-        Arc::new(RwLock::new(ProductEditor::new(depth, ctx.clone())
+        
+        let a = Arc::new(RwLock::new(ProductEditor::new(depth, ctx.clone())
                              .with_n(Point2::new(0, 0), vec![ ctx.read().unwrap().type_term_from_str("( String )").unwrap() ] )
 
-        )) as Arc<RwLock<dyn TerminalTreeEditor + Send + Sync>>
+        )) as Arc<RwLock<dyn Nested + Send + Sync>>;
+
+        let b = Arc::new(RwLock::new(ProductEditor::new(depth, ctx.clone())
+                             .with_n(Point2::new(0, 0), vec![ ctx.read().unwrap().type_term_from_str("( PosInt 16 BigEndian )").unwrap() ] )
+
+        )) as Arc<RwLock<dyn Nested + Send + Sync>>;
+
+        let mut x = Arc::new(RwLock::new( SumEditor::new(
+            vec![
+                a, b
+            ]
+        )  ));
+
+        x.write().unwrap().select(0);
+        x
     }
 }
 
 pub struct ActCp {}
 impl Action for ActCp {
-    fn make_editor(&self, ctx: Arc<RwLock<Context>>) -> Arc<RwLock<dyn TerminalTreeEditor + Send + Sync>> {
+    fn make_editor(&self, ctx: Arc<RwLock<Context>>) -> Arc<RwLock<dyn Nested + Send + Sync>> {
         let depth = 1;
         Arc::new(RwLock::new(ProductEditor::new(depth, ctx.clone())
                              .with_t(Point2::new(1, 1), " Source")
@@ -73,13 +90,13 @@ impl Action for ActCp {
                              .with_n(Point2::new(0, 2), vec![ ctx.read().unwrap().type_term_from_str("( Path )").unwrap() ] )
                              .with_t(Point2::new(1, 3), " Options")
                              .with_n(Point2::new(0, 3), vec![ ctx.read().unwrap().type_term_from_str("( List Symbol )").unwrap() ] )
-        )) as Arc<RwLock<dyn TerminalTreeEditor + Send + Sync>>
+        )) as Arc<RwLock<dyn Nested + Send + Sync>>
     }
 }
 
 pub struct ActNum {}
 impl Action for ActNum {
-    fn make_editor(&self, ctx: Arc<RwLock<Context>>) -> Arc<RwLock<dyn TerminalTreeEditor + Send + Sync>> {
+    fn make_editor(&self, ctx: Arc<RwLock<Context>>) -> Arc<RwLock<dyn Nested + Send + Sync>> {
         let depth = 1;
         Arc::new(RwLock::new(ProductEditor::new(depth, ctx.clone())
                              .with_t(Point2::new(1, 1), " Value")
@@ -87,7 +104,7 @@ impl Action for ActNum {
                              .with_t(Point2::new(1, 2), " Radix")
                              .with_n(Point2::new(0, 2), vec![ ctx.read().unwrap().type_term_from_str("( PosInt 10 BigEndian )").unwrap() ] )
 
-    )) as Arc<RwLock<dyn TerminalTreeEditor + Send + Sync>>
+    )) as Arc<RwLock<dyn Nested + Send + Sync>>
 
 //        Arc::new(RwLock::new(nested::integer::PosIntEditor::new(10)))
     }
@@ -95,7 +112,7 @@ impl Action for ActNum {
 
 pub struct ActColor {}
 impl Action for ActColor {
-    fn make_editor(&self, ctx: Arc<RwLock<Context>>) -> Arc<RwLock<dyn TerminalTreeEditor + Send + Sync>> {
+    fn make_editor(&self, ctx: Arc<RwLock<Context>>) -> Arc<RwLock<dyn Nested + Send + Sync>> {
         let depth = 1;
         Arc::new(RwLock::new(ProductEditor::new(depth, ctx.clone())
                              .with_t(Point2::new(1, 1), " RGB")
@@ -104,19 +121,19 @@ impl Action for ActColor {
                              .with_n(Point2::new(0, 2), vec![ ctx.read().unwrap().type_term_from_str("( RGB )").unwrap() ] )
                              .with_t(Point2::new(1, 3), " HSL")
                              .with_n(Point2::new(0, 3), vec![ ctx.read().unwrap().type_term_from_str("( RGB )").unwrap() ] )
-        )) as Arc<RwLock<dyn TerminalTreeEditor + Send + Sync>>
+        )) as Arc<RwLock<dyn Nested + Send + Sync>>
     }
 }
 
 pub struct ActLet {}
 impl Action for ActLet {
-    fn make_editor(&self, ctx: Arc<RwLock<Context>>) -> Arc<RwLock<dyn TerminalTreeEditor + Send + Sync>> {
+    fn make_editor(&self, ctx: Arc<RwLock<Context>>) -> Arc<RwLock<dyn Nested + Send + Sync>> {
         let depth = 1;
         Arc::new(RwLock::new(ProductEditor::new(depth, ctx.clone())
                              .with_n(Point2::new(0, 0), vec![ ctx.read().unwrap().type_term_from_str("( Symbol )").unwrap() ] )
                              .with_t(Point2::new(1, 0), " := ")
                              .with_n(Point2::new(2, 0), vec![ ctx.read().unwrap().type_term_from_str("( PosInt 10 BigEndian )").unwrap() ] )
-        )) as Arc<RwLock<dyn TerminalTreeEditor + Send + Sync>>
+        )) as Arc<RwLock<dyn Nested + Send + Sync>>
     }
 }
 
@@ -127,7 +144,7 @@ pub struct Commander {
     valid: Arc<RwLock<bool>>,
     confirmed: bool,
     symbol_editor: PTYListEditor<CharEditor>,
-    cmd_editor: Option<Arc<RwLock<dyn TerminalTreeEditor + Send + Sync>>>,
+    cmd_editor: Option<Arc<RwLock<dyn Nested + Send + Sync>>>,
 
     view_elements: VecBuffer<OuterViewPort<dyn TerminalView>>,
     out_port: OuterViewPort<dyn TerminalView>,
@@ -209,9 +226,12 @@ impl TerminalEditor for Commander {
         if let (Some(cmd_editor), true) = (self.cmd_editor.as_ref(), self.confirmed) {
             match event {
                 TerminalEvent::Input(Event::Key(Key::Char('\n'))) => {
-                    if cmd_editor.write().unwrap().nexd() == TreeNavResult::Exit {
+                    let mut c = cmd_editor.write().unwrap();
+                    if let TerminalEditorResult::Exit = c.handle_terminal_event(&TerminalEvent::Input(Event::Key(Key::Char('\n')))) {
+
                         // run
-                        cmd_editor.write().unwrap().goto(TreeCursor::none());
+                        c.goto(TreeCursor::none());
+                        c.up();
 
                         TerminalEditorResult::Exit
                     } else {
@@ -245,7 +265,7 @@ impl TerminalEditor for Commander {
                         self.m_buf.clear();
                         self.m_buf.push(b.get_port().to_sequence());
                     }
-
+                    
                     TerminalEditorResult::Continue
                 }
 
@@ -323,5 +343,5 @@ impl TreeNav for Commander {
     }
 }
 
-impl TerminalTreeEditor for Commander {}
+impl Nested for Commander {}
 
diff --git a/shell/src/main.rs b/shell/src/main.rs
index 75dc2a1..c380af0 100644
--- a/shell/src/main.rs
+++ b/shell/src/main.rs
@@ -22,10 +22,11 @@ use {
             make_label, Terminal, TerminalAtom, TerminalCompositor, TerminalEditor,
             TerminalEditorResult, TerminalEvent, TerminalStyle, TerminalView,
         },
-        tree_nav::{TreeNav, TerminalTreeEditor, TreeCursor, TreeNavResult},
+        tree::{TreeNav, TreeCursor, TreeNavResult},
         vec::VecBuffer,
         integer::{PosIntEditor},
-        diagnostics::{Diagnostics}
+        diagnostics::{Diagnostics},
+        Nested
     },
     std::sync::{Arc, RwLock},
     termion::event::{Event, Key},
diff --git a/shell/src/process.rs b/shell/src/process.rs
index 8fa456c..a25f1fc 100644
--- a/shell/src/process.rs
+++ b/shell/src/process.rs
@@ -10,8 +10,9 @@ use {
             TerminalAtom, TerminalEditor, TerminalEditorResult, TerminalEvent, TerminalStyle,
             TerminalView,
         },
-        tree_nav::{TerminalTreeEditor, TreeCursor, TreeNav, TreeNavResult},
-        diagnostics::Diagnostics
+        tree::{TreeCursor, TreeNav, TreeNavResult},
+        diagnostics::Diagnostics,
+        Nested
     },
     std::sync::Arc,
     std::sync::RwLock,
@@ -77,7 +78,7 @@ impl TreeNav for ProcessArg {
 impl Diagnostics for ProcessArg {    
 }
 
-impl TerminalTreeEditor for ProcessArg {}
+impl Nested for ProcessArg {}
 
 pub struct ProcessLauncher {
     cmd_editor: PTYListEditor<ProcessArg>,
@@ -272,5 +273,5 @@ impl TreeNav for ProcessLauncher {
 impl Diagnostics for ProcessLauncher {
 }
 
-impl TerminalTreeEditor for ProcessLauncher {}
+impl Nested for ProcessLauncher {}