diff --git a/examples/tty-02-node/src/main.rs b/examples/tty-02-node/src/main.rs
index b44d2bf..7e40c63 100644
--- a/examples/tty-02-node/src/main.rs
+++ b/examples/tty-02-node/src/main.rs
@@ -8,17 +8,19 @@ use {
     cgmath::Vector2,
     nested::{
         editors::ObjCommander,
-        repr_tree::{Context, ReprTree},
+        repr_tree::{Context, ReprTree, ReprTreeExt},
         edit_tree::{EditTree}
     },
     nested_tty::{
         DisplaySegment, TTYApplication,
         TerminalCompositor, TerminalStyle, TerminalView,
-        TerminalAtom
+        TerminalAtom, TerminalEvent
     },
     r3vi::{
         buffer::{singleton::*, vec::*},
+        view::{port::UpdateTask}
     },
+//    termion::{},
     std::sync::{Arc, RwLock},
 };
 
@@ -48,8 +50,8 @@ async fn main() {
     // It provides the necessary bridge to the rendering- & input-backend.
     ctx.write().unwrap().set_edittree_hook(
         Arc::new(
-            move |et: Arc<RwLock<EditTree>>, t: laddertypes::TypeTerm| {
-                let mut et = et.write().unwrap();
+            move |et: &mut EditTree, t: laddertypes::TypeTerm| {
+//                let mut et = et.write().unwrap();
 
                 if let Ok(σ) = laddertypes::unify(&t, &char_type.clone()) {
                     *et = nested_tty::editors::edittree_make_char_view(et.clone());
@@ -95,31 +97,49 @@ async fn main() {
      *                         /     |      \
      *                       TTY  PixelBuf  SDF
      */
-   let rt_digit = ReprTree::new_arc( Context::parse(&ctx, "<Digit 16>") );
+    let mut rt_digit = ReprTree::new_arc( Context::parse(&ctx, "<Digit 16>") );
 
     /* add initial representation
      *  <Digit 16> ~ Char
      */
-    rt_digit.write().unwrap()
-        .insert_leaf(
-            vec![ Context::parse(&ctx, "Char") ].into_iter(),
-            SingletonBuffer::new('4').get_port().into()
-        );
+    rt_digit.insert_leaf(
+        Context::parse(&ctx, "Char"),
+        nested::repr_tree::ReprLeaf::from_singleton_buffer( SingletonBuffer::new('5') )
+    );
+
+    /* furthermore, setup projections to and from u8 value,
+     * this synchronizes the buffers 
+     */
+    ctx.read().unwrap().morphisms.apply_morphism(
+        rt_digit.clone(),
+        &Context::parse(&ctx, "<Digit 16>~Char"),
+        &Context::parse(&ctx, "<Digit 16>~ℤ_256~machine::UInt8")
+    );
 
     /* setup TTY-Display for DigitEditor
+     *
+     * `setup_edittree` will setup the projection
+     *    Char -> Char~EditTree
+     *  and call the hook defined above with `set_edittree_hook()`
+     *
      */
     let edittree_digit = ctx.read().unwrap()
         .setup_edittree(
-            rt_digit
-                .read().unwrap()
-                .descend( Context::parse(&ctx, "Char") ).unwrap()
-                .clone(),
-            r3vi::buffer::singleton::SingletonBuffer::new(0).get_port());
+            rt_digit.clone(),
+            r3vi::buffer::singleton::SingletonBuffer::new(0).get_port()
+        );
+
+    let mut digit_u8_buffer = rt_digit
+        .descend(Context::parse(&ctx, "ℤ_256~machine::UInt8")).unwrap()
+        .singleton_buffer::<u8>();
 
     //---
-    let rt_string = ReprTree::new_arc( Context::parse(&ctx, "<List <Digit 10>>") );
-    let edittree = ctx.read().unwrap()
-        .setup_edittree(rt_string.clone(), r3vi::buffer::singleton::SingletonBuffer::new(0).get_port());
+    let rt_string = ReprTree::new_arc( Context::parse(&ctx, "<List Char>") );
+
+    let edittree_list = ctx.read().unwrap()
+        .setup_edittree(
+            rt_string.clone(),
+            r3vi::buffer::singleton::SingletonBuffer::new(0).get_port());
 
     /* setup terminal
      */
@@ -127,9 +147,22 @@ async fn main() {
         /* event handler
          */
         let ctx = ctx.clone();
-        let et1 = edittree.clone();
+        let mut editors = Vec::new();
+        editors.push(edittree_digit.clone());
+        editors.push(edittree_list.clone());
+
+        let edit_select = Arc::new(RwLock::new(0));
         move |ev| {
-            et1.write().unwrap().send_cmd_obj(ev.to_repr_tree(&ctx));
+            match ev {
+                TerminalEvent::Input(termion::event::Event::Key(termion::event::Key::Char('\t'))) => {
+                    let mut i = edit_select.write().unwrap();
+                    *i = (*i + 1) % editors.len();
+                }
+                _ => {
+                    let i = edit_select.read().unwrap();
+                    editors[*i].get().send_cmd_obj(ev.to_repr_tree(&ctx));
+                }
+            }
         }
     });
 
@@ -150,25 +183,37 @@ async fn main() {
         );
 
         comp.push(
-            edittree_digit.read().unwrap().display_view()
-            .offset(Vector2::new(0,2))
+            edittree_digit.get().display_view()
+            .offset(Vector2::new(2,2))
         );
 
         let label_str = ctx.read().unwrap().type_term_to_str(&rt_digit.read().unwrap().get_type());
         comp.push(
             nested_tty::make_label(&label_str)
+            .map_item(|_pt,atom| atom.add_style_front(TerminalStyle::fg_color((90,90,90))))
             .offset(Vector2::new(0, 1))
         );
 
         comp.push(
-            edittree.read().unwrap().display_view()
-            .offset(Vector2::new(0,4))
+            digit_u8_buffer.get_port().map(
+                |d| nested_tty::make_label(&format!("Digit={}", d))
+            )
+            .to_grid()
+            .flatten()
+            .offset(Vector2::new(2,3))
+        );
+
+
+        comp.push(
+            edittree_list.get().display_view()
+            .offset(Vector2::new(2,6))
         );
 
         let label_str = ctx.read().unwrap().type_term_to_str(&rt_string.read().unwrap().get_type());
         comp.push(
             nested_tty::make_label(&label_str)
-            .offset(Vector2::new(0, 3))
+            .map_item(|_pt, atom| atom.add_style_front(TerminalStyle::fg_color((90,90,90))))
+            .offset(Vector2::new(0, 5))
         );
     }
 
diff --git a/lib-nested-core/src/editors/char/mod.rs b/lib-nested-core/src/editors/char/mod.rs
index d6a4d07..8b587ad 100644
--- a/lib-nested-core/src/editors/char/mod.rs
+++ b/lib-nested-core/src/editors/char/mod.rs
@@ -3,12 +3,13 @@ use {
         view::{
             OuterViewPort,
             singleton::*,
+            port::UpdateTask
         },
         buffer::singleton::*
     },
     laddertypes::{TypeTerm},
     crate::{
-        repr_tree::{Context, ReprTree},
+        repr_tree::{Context, ReprTree, ReprTreeExt},
         edit_tree::{EditTree, TreeNavResult},
         editors::ObjCommander,
     },
@@ -17,7 +18,6 @@ use {
 };
 
 pub fn init_ctx( ctx: Arc<RwLock<Context>> ) {
-    
     let morphtype =
             crate::repr_tree::MorphismType {
                 src_type: Context::parse(&ctx, "Char"),
@@ -37,19 +37,25 @@ pub fn init_ctx( ctx: Arc<RwLock<Context>> ) {
 
                     /* Create EditTree object
                      */
-                    let mut edittree_char = CharEditor::new_edit_tree(
+                    rt.view_char().0.update();
+
+                    let char_buf = rt.write().unwrap().singleton_buffer::<char>().unwrap();
+
+                    eprintln!("make edittree: char val = {}", char_buf.get());
+                    let mut edittree = CharEditor::new_edit_tree(
                         ctx.clone(),
-                        SingletonBuffer::new('>'),
+                        char_buf,
                         r3vi::buffer::singleton::SingletonBuffer::<usize>::new(0).get_port()
                     );
 
-                    /* Insert EditTree into ReprTree
-                     */
-                    let mut rt = rt.write().unwrap();
-                    rt.insert_leaf(
-                        vec![ Context::parse(&ctx, "EditTree") ].into_iter(),
-                        SingletonBuffer::new( Arc::new(RwLock::new( edittree_char )) ).get_port().into()
-                    );
+                    eprintln!("insert Char~EditTree");
+                    rt.write().unwrap()
+                        .insert_branch(
+                            ReprTree::from_singleton_buffer(
+                                Context::parse(&ctx, "EditTree"),
+                                SingletonBuffer::new(edittree)
+                            )
+                        );
                 }
             }
         );
@@ -105,7 +111,7 @@ impl CharEditor {
         data: SingletonBuffer<char>,
         depth: OuterViewPort<dyn SingletonView<Item = usize>>
     ) -> EditTree {
-        let data = SingletonBuffer::new('\0');
+        //let data = SingletonBuffer::new('\0');
         let ctx = ctx0.clone();
         let editor = Arc::new(RwLock::new(CharEditor{ ctx, data: data.clone() }));
 
diff --git a/lib-nested-core/src/editors/digit/cmd.rs b/lib-nested-core/src/editors/digit/cmd.rs
new file mode 100644
index 0000000..ae56f9f
--- /dev/null
+++ b/lib-nested-core/src/editors/digit/cmd.rs
@@ -0,0 +1,52 @@
+
+use {
+    r3vi::view::singleton::SingletonView,
+    crate::{
+        repr_tree::{ReprTree, Context},
+        edit_tree::{TreeNav, TreeNavResult},
+        editors::{ObjCommander, digit::DigitEditor}
+    },
+
+    std::sync::{Arc, RwLock}
+};
+
+impl ObjCommander for DigitEditor {
+    fn send_cmd_obj(&mut self, cmd_obj: Arc<RwLock<ReprTree>>) -> TreeNavResult {
+        let cmd_obj = cmd_obj.read().unwrap();
+        let cmd_type = cmd_obj.get_type().clone();
+
+        if cmd_type == Context::parse(&self.ctx, "Char") {
+            if let Some(cmd_view) = cmd_obj.get_view::<dyn SingletonView<Item = char>>() {
+                let c = cmd_view.get();
+
+                self.msg.clear();
+
+                if self.ctx.read().unwrap().meta_chars.contains(&c) {
+                    return TreeNavResult::Exit;
+
+                } else if c.to_digit(self.radix).is_none() {
+                    /* in case the character c is not in the range of digit-chars,
+                       add a message to the diagnostics view
+                     */
+/*
+                    let message = IndexBuffer::from_iter(vec![
+                        (Point2::new(1, 0), make_label("invalid digit '")),
+                        (Point2::new(2, 0), make_label(&format!("{}", c))
+                         .map_item(|_p,a| a.add_style_back(TerminalStyle::fg_color((140,140,250))))),
+                        (Point2::new(3, 0), make_label("'"))
+                    ]);
+
+                    self.msg.push(crate::diagnostics::make_error(message.get_port().flatten()));
+*/
+
+                    self.data.set(c);
+                } else {
+                    self.data.set(c);
+                }
+            }
+        }
+
+        TreeNavResult::Continue
+    }
+}
+
diff --git a/lib-nested-core/src/editors/digit/ctx.rs b/lib-nested-core/src/editors/digit/ctx.rs
new file mode 100644
index 0000000..bb022a7
--- /dev/null
+++ b/lib-nested-core/src/editors/digit/ctx.rs
@@ -0,0 +1,149 @@
+
+use {
+    laddertypes::TypeTerm,
+    r3vi::{
+        buffer::singleton::SingletonBuffer,
+        view::{
+            AnyOuterViewPort,
+            singleton::*
+        }
+    },
+    crate::{
+        repr_tree::{Context, ReprTree, ReprTreeExt, ReprLeaf},
+        editors::digit::DigitEditor,
+    },
+    std::sync::{Arc, RwLock}
+};
+
+pub fn init_ctx( ctx: Arc<RwLock<Context>> ) {
+
+    // todo: proper scoping of Radix variable
+    ctx.write().unwrap().add_varname("Radix");
+
+    let morphtype =
+            crate::repr_tree::MorphismType {
+                src_type: Context::parse(&ctx, "<Digit Radix>"),
+                dst_type: Context::parse(&ctx, "<Digit Radix>~EditTree")
+            };
+
+    ctx.write().unwrap()
+        .morphisms
+        .add_morphism(
+            morphtype,
+            {
+                let ctx = ctx.clone();
+                move |src_rt, σ| {
+                    let radix =
+                        match σ.get( &laddertypes::TypeID::Var(ctx.read().unwrap().get_var_typeid("Radix").unwrap()) ) {
+                            Some(TypeTerm::Num(n)) => *n as u32,
+                            _ => 0
+                        };
+
+                    /* Create EditTree object
+                     */
+                    let mut edittree = DigitEditor::new(
+                        ctx.clone(),
+                        radix,
+                        src_rt.descend(
+                            Context::parse(&ctx, "Char")
+                        ).unwrap()
+                        .singleton_buffer::<char>()
+                    ).into_node(
+                        r3vi::buffer::singleton::SingletonBuffer::<usize>::new(0).get_port()
+                    );
+
+                    src_rt.write().unwrap()
+                        .insert_branch(
+                            ReprTree::from_singleton_buffer(
+                                Context::parse(&ctx, "EditTree"),
+                                SingletonBuffer::new(edittree)
+                            )
+                        );
+                }
+            }
+        );
+
+    let morphtype =
+            crate::repr_tree::MorphismType {
+                src_type: Context::parse(&ctx, "<Digit Radix>~Char"),
+                dst_type: Context::parse(&ctx, "<Digit Radix>~ℤ_256~machine::UInt8")
+            };
+
+    ctx.write().unwrap()
+        .morphisms
+        .add_morphism(
+            morphtype,
+            {
+                let ctx = ctx.clone();
+                move |rt: &mut Arc<RwLock<ReprTree>>, σ: &std::collections::HashMap<laddertypes::TypeID, TypeTerm>| {
+                    /* infer radix from type
+                     */
+                    let radix =
+                        match σ.get( &laddertypes::TypeID::Var(ctx.read().unwrap().get_var_typeid("Radix").unwrap()) ) {
+                            Some(TypeTerm::Num(n)) => (*n) as u32,
+                            _ => 0
+                        };
+
+                    if radix <= 256 {
+
+                        if let Some(src_rt) = rt.descend(Context::parse(&ctx, "Char")) {
+                            /* insert projected view into ReprTree
+                             */
+                            let u8_view = 
+                                    src_rt.view_char()
+                                        .map(move |c| c.to_digit(radix).unwrap_or(0) as u8);
+
+                            rt.write().unwrap().attach_leaf_to::<dyn SingletonView<Item = u8>>(
+                                Context::parse(&ctx, "ℤ_256~machine::UInt8").get_lnf_vec().into_iter(),
+                                u8_view
+                            );
+                        } else {
+                            eprintln!("could not find required source representation: <Digit {}>~Char", radix);
+                        }
+                    } else {
+                        eprintln!("radix too large ({})", radix);
+                    }
+                }
+            }
+        );
+
+
+    let morphtype =
+            crate::repr_tree::MorphismType {
+                src_type: Context::parse(&ctx, "<Digit Radix>~ℤ_256~machine::UInt8"),
+                dst_type: Context::parse(&ctx, "<Digit Radix>~Char")
+            };
+
+    ctx.write().unwrap().morphisms
+        .add_morphism(morphtype, {
+            let ctx = ctx.clone();
+            move |rt: &mut Arc<RwLock<ReprTree>>, σ: &std::collections::HashMap<laddertypes::TypeID, TypeTerm>| {
+                /* infer radix from type
+                 */
+                let radix =
+                    match σ.get( &laddertypes::TypeID::Var(ctx.read().unwrap().get_var_typeid("Radix").unwrap()) ) {
+                       Some(TypeTerm::Num(n)) => (*n) as u32,
+                        _ => 0
+                    };
+
+                if radix <= 256 {
+                    /* insert projected view into ReprTree
+                     */
+                    let char_view = 
+                        rt.descend(Context::parse(&ctx, "ℤ_256~machine::UInt8"))
+                            .unwrap()
+                            .view_u8()
+                            .map(move |digit| char::from_digit(digit as u32, radix).unwrap_or('?'));
+
+                    rt.write().unwrap().attach_leaf_to::<dyn SingletonView<Item = char>>(
+                        Context::parse(&ctx, "Char").get_lnf_vec().into_iter(),
+                        char_view
+                    );
+                } else {
+                    eprintln!("radix too large ({})", radix);
+                }
+            }
+        });
+}
+
+
diff --git a/lib-nested-core/src/editors/digit/editor.rs b/lib-nested-core/src/editors/digit/editor.rs
new file mode 100644
index 0000000..a73733b
--- /dev/null
+++ b/lib-nested-core/src/editors/digit/editor.rs
@@ -0,0 +1,89 @@
+
+use {
+    laddertypes::TypeTerm,
+    r3vi::{
+        view::{OuterViewPort,singleton::*},
+        buffer::{singleton::*, vec::*}
+    },
+    crate::{
+        repr_tree::{ReprTree, Context},
+        edit_tree::{
+            EditTree,
+            diagnostics::Message
+        }
+    },
+
+    std::sync::{Arc, RwLock}
+};
+
+
+pub struct DigitEditor {
+    pub(super) ctx: Arc<RwLock<Context>>,
+    pub(super) radix: u32,
+    pub(super) data: SingletonBuffer<char>,
+    pub(super) msg: VecBuffer<Message>,
+}
+
+
+impl DigitEditor {
+    pub fn new(ctx: Arc<RwLock<Context>>, radix: u32, data: SingletonBuffer<char>) -> Self {
+        DigitEditor {
+            ctx,
+            radix,
+            data,
+            msg: VecBuffer::new(),
+        }
+    }
+
+    pub fn into_node(self, depth: OuterViewPort<dyn SingletonView<Item = usize>>) -> EditTree { 
+      //  let data = self.get_data();        
+        let editor = Arc::new(RwLock::new(self));
+        let ed = editor.write().unwrap();
+        let r = ed.radix;
+
+        EditTree::new(ed.ctx.clone(), depth)
+            .set_editor(editor.clone())
+            .set_cmd(editor.clone())
+            .set_diag(
+                ed.msg.get_port().to_sequence()
+            )
+    }
+
+    pub fn attach_to(&mut self, source: OuterViewPort<dyn SingletonView<Item = u32>>) {
+        /*
+        source.add_observer(
+            Arc::new(NotifyFnObserver::new(|_msg| {
+                self.data.set( source.get() )
+            }))
+        );
+        */
+    }
+
+    pub fn get_data_port(&self) -> OuterViewPort<dyn SingletonView<Item = Result<u32, char>>> {
+        let radix = self.radix;
+        self.data.get_port().map(move |c|
+            if let Some(d) = c.to_digit(radix) {
+                Ok(d)
+            } else {
+                Err(c)
+            }
+        )
+    }
+
+    pub fn get_type(&self) -> TypeTerm {
+        TypeTerm::TypeID(self.ctx.read().unwrap().get_typeid("Digit").unwrap())
+    }
+/*
+    pub fn get_data(&self) -> Arc<RwLock<ReprTree>> {
+        ReprTree::ascend(
+            &ReprTree::from_view(
+                self.ctx.read().unwrap().type_term_from_str("<Seq u32>").unwrap(),
+                self.get_data_port()
+            ),
+            self.get_type()
+        )
+    }
+    */
+}
+
+
diff --git a/lib-nested-core/src/editors/digit/mod.rs b/lib-nested-core/src/editors/digit/mod.rs
new file mode 100644
index 0000000..980db26
--- /dev/null
+++ b/lib-nested-core/src/editors/digit/mod.rs
@@ -0,0 +1,8 @@
+
+pub mod ctx;
+pub mod cmd;
+pub mod editor;
+
+pub use editor::DigitEditor;
+pub use ctx::init_ctx;
+
diff --git a/lib-nested-core/src/editors/list/cmd.rs b/lib-nested-core/src/editors/list/cmd.rs
index 4c37ae0..bbdd19c 100644
--- a/lib-nested-core/src/editors/list/cmd.rs
+++ b/lib-nested-core/src/editors/list/cmd.rs
@@ -24,10 +24,9 @@ pub enum ListCmd {
 impl ListCmd {
     // note: cant use Into becaue of ctx (maybe global typedict?)
     pub fn into_repr_tree(self, ctx: &Arc<RwLock<Context>>) -> Arc<RwLock<ReprTree>> {
-        let buf = r3vi::buffer::singleton::SingletonBuffer::new(self);
-        ReprTree::new_leaf(
-            Context::parse(ctx, "ListCmd"),
-            buf.get_port().into()
+        ReprTree::from_singleton_buffer(
+            Context::parse(ctx, "ListCmd"),            
+            r3vi::buffer::singleton::SingletonBuffer::new(self)
         )
     }
 }
diff --git a/lib-nested-core/src/editors/list/ctx.rs b/lib-nested-core/src/editors/list/ctx.rs
index 0ef2180..3c3ae8f 100644
--- a/lib-nested-core/src/editors/list/ctx.rs
+++ b/lib-nested-core/src/editors/list/ctx.rs
@@ -2,7 +2,7 @@ use {
     r3vi::{view::{OuterViewPort, singleton::*}, buffer::singleton::*},
     laddertypes::{TypeTerm},
     crate::{
-        repr_tree::{Context},
+        repr_tree::{Context, ReprTree},
         editors::list::{ListEditor}//, PTYListController, PTYListStyle}
     },
     std::sync::{Arc, RwLock}
@@ -13,6 +13,7 @@ use {
 pub fn init_ctx(ctx: Arc<RwLock<Context>>) {
     ctx.write().unwrap().add_list_typename("List".into());
     ctx.write().unwrap().add_varname("Item");
+
     let mt = crate::repr_tree::MorphismType {
         src_type: Context::parse(&ctx, "<List Item>"),
         dst_type: Context::parse(&ctx, "<List Item>~EditTree")
@@ -21,9 +22,10 @@ pub fn init_ctx(ctx: Arc<RwLock<Context>>) {
         mt,
         {
             let ctx = ctx.clone();
-            move |rt, σ| {
+            move |src_rt, σ| {
                 let item_id = laddertypes::TypeID::Var( ctx.read().unwrap().get_var_typeid("Item").unwrap() );
                 if let Some( item_type ) = σ.get( &item_id ) {
+
                     let mut edittree_list = ListEditor::new(
                         ctx.clone(),
                         item_type.clone()
@@ -31,10 +33,11 @@ pub fn init_ctx(ctx: Arc<RwLock<Context>>) {
                         r3vi::buffer::singleton::SingletonBuffer::<usize>::new(0).get_port()
                     );
 
-                    let mut rt = rt.write().unwrap();
-                    rt.insert_leaf(
-                        vec![ Context::parse(&ctx, "EditTree") ].into_iter(),
-                        SingletonBuffer::new( Arc::new(RwLock::new( edittree_list )) ).get_port().into()
+                    src_rt.write().unwrap().insert_branch(
+                        ReprTree::from_singleton_buffer(
+                            Context::parse(&ctx, "EditTree"),
+                            SingletonBuffer::new(edittree_list)
+                        )
                     );
                 } else {
                     eprintln!("no item type");
diff --git a/lib-nested-core/src/editors/list/editor.rs b/lib-nested-core/src/editors/list/editor.rs
index f0e7cb7..00020e7 100644
--- a/lib-nested-core/src/editors/list/editor.rs
+++ b/lib-nested-core/src/editors/list/editor.rs
@@ -101,7 +101,6 @@ impl ListEditor {
     }
 
     pub fn into_node(mut self, depth: OuterViewPort<dyn SingletonView<Item = usize>>) -> EditTree {
-        let data = self.get_data();
         let ctx = self.ctx.clone();
 
         self.depth = depth.clone();
@@ -155,7 +154,7 @@ impl ListEditor {
             |x| x.read().unwrap().clone()
         )
     }
-
+/*
     pub fn get_data(&self) -> Arc<RwLock<ReprTree>> {
         let data_view = self.get_data_port();
         ReprTree::new_leaf(
@@ -163,7 +162,7 @@ impl ListEditor {
             data_view.into()
         )
     }
-
+*/
     pub fn get_item(&self) -> Option<EditTree> {
         if let Some(idx) = self.cursor.get().idx {
             let idx = crate::utils::modulo(idx as isize, self.data.len() as isize) as usize;
@@ -309,22 +308,23 @@ impl ListEditor {
                 let mut b = item.ctrl.spillbuf.write().unwrap();
 
                 let rt = ReprTree::new_arc(self.typ.clone());
-                let new_edittree = self.ctx.read().unwrap()
+                let edittree = self.ctx.read().unwrap()
                     .setup_edittree(
                         rt,
                         self.depth.map(|d| d+1)
                     );
-                let mut tail_node = new_edittree.write().unwrap();
+
+                let mut tail_node = edittree.get_mut();
                 tail_node.goto(TreeCursor::home());
 
                 for node in b.iter() {
                     tail_node
                         .send_cmd_obj(
-                            ReprTree::new_leaf(
-                                Context::parse(&self.ctx, "NestedNode"),
+                            ReprTree::from_singleton_buffer(
+                                Context::parse(&self.ctx, "EditTree"),
                                 SingletonBuffer::<EditTree>::new(
                                     node.read().unwrap().clone()
-                                ).get_port().into()
+                                )
                             )
                         );
                 }
@@ -340,7 +340,7 @@ impl ListEditor {
                 drop(tail_node);
 
                 self.insert(
-                    new_edittree
+                    edittree.value.clone()
                 );
 
             } else {
@@ -376,11 +376,11 @@ impl ListEditor {
             let data = cur_editor.ctrl.spillbuf.read().unwrap();
             for x in data.iter() {
                 pxv_editor.send_cmd_obj(
-                    ReprTree::new_leaf(
-                        Context::parse(&self.ctx, "NestedNode"),
+                    ReprTree::from_singleton_buffer(
+                        Context::parse(&self.ctx, "EditTree"),
                         SingletonBuffer::<EditTree>::new(
                             x.read().unwrap().clone()
-                        ).get_port().into()
+                        )
                     )
                 );
             }
@@ -435,11 +435,11 @@ impl ListEditor {
 
             for x in data.iter() {
                 cur_editor.send_cmd_obj(
-                    ReprTree::new_leaf(
-                        Context::parse(&self.ctx, "NestedNode"),
+                    ReprTree::from_singleton_buffer(
+                        Context::parse(&self.ctx, "EditTree"),
                         SingletonBuffer::<EditTree>::new(
                             x.read().unwrap().clone()
-                        ).get_port().into()
+                        )
                     )
                 );
             }
diff --git a/lib-nested-core/src/repr_tree/context.rs b/lib-nested-core/src/repr_tree/context.rs
index ef07efe..abd23ff 100644
--- a/lib-nested-core/src/repr_tree/context.rs
+++ b/lib-nested-core/src/repr_tree/context.rs
@@ -2,7 +2,7 @@ use {
     r3vi::{view::{OuterViewPort, singleton::*}, buffer::{singleton::*}},
     laddertypes::{TypeDict, TypeTerm, TypeID},
     crate::{
-        repr_tree::{ReprTree, MorphismType, GenericReprTreeMorphism, MorphismBase},
+        repr_tree::{ReprTree, ReprTreeExt, MorphismType, GenericReprTreeMorphism, MorphismBase},
         edit_tree::EditTree
     },
     std::{
@@ -29,7 +29,7 @@ pub struct Context {
     pub list_types: Vec< TypeID >,
     pub meta_chars: Vec< char >,
 
-    edittree_hook: Arc< dyn Fn(Arc<RwLock<EditTree>>, TypeTerm) + Send +Sync +'static >,
+    edittree_hook: Arc< dyn Fn(&mut EditTree, TypeTerm) + Send +Sync +'static >,
 
     /// recursion
     parent: Option<Arc<RwLock<Context>>>,
@@ -64,7 +64,7 @@ impl Context {
         Context::with_parent(None)
     }
 
-    pub fn set_edittree_hook(&mut self, hook: Arc< dyn Fn(Arc<RwLock<EditTree>>, TypeTerm) + Send +Sync +'static >) {
+    pub fn set_edittree_hook(&mut self, hook: Arc< dyn Fn(&mut EditTree, TypeTerm) + Send +Sync +'static >) {
         self.edittree_hook = hook;
     }
 
@@ -78,7 +78,7 @@ impl Context {
 
     pub fn make_repr(ctx: &Arc<RwLock<Self>>, t: &TypeTerm) -> Arc<RwLock<ReprTree>> {
         let rt = Arc::new(RwLock::new(ReprTree::new( TypeTerm::unit() )));
-        ctx.read().unwrap().morphisms.morph( rt.clone(), t );
+        ctx.read().unwrap().morphisms.apply_morphism( rt.clone(), &TypeTerm::unit(), t );
         rt
     }
 
@@ -180,30 +180,32 @@ impl Context {
         &self,
         rt: Arc<RwLock<ReprTree>>,
         depth: OuterViewPort<dyn SingletonView<Item = usize>>
-    ) -> Arc<RwLock<EditTree>> {
+    ) -> SingletonBuffer<EditTree> {
         let ladder = TypeTerm::Ladder(vec![
                 rt.read().unwrap().get_type().clone(),
                 self.type_term_from_str("EditTree").expect("")
             ]);
-        
-        self.morphisms.morph(
+
+        eprintln!("setp_edittree: apply morphism T -> T~EditTree");
+        self.morphisms.apply_morphism(
             rt.clone(),
+            &rt.get_type(),
             &ladder
         );
 
-        let new_edittree = rt
-            .read().unwrap()
-            .descend(
-            self.type_term_from_str("EditTree").expect("")
-        ).unwrap()
-            .read().unwrap()
-            .get_view::<dyn SingletonView<Item = Arc<RwLock<EditTree>> >>()
-            .unwrap()
-            .get();
-
-        (*self.edittree_hook)( new_edittree.clone(), rt.read().unwrap().get_type().clone() );
-
-        new_edittree
+        eprintln!("get repr-node of editTree");
+        if let Some(new_edittree) =
+            rt.descend(self.type_term_from_str("EditTree").unwrap())
+        {
+            let buf = new_edittree.singleton_buffer::<EditTree>();
+            (*self.edittree_hook)(
+                &mut *buf.get_mut(),
+                rt.read().unwrap().get_type().clone()
+            );
+            buf
+        } else {
+            unreachable!();
+        }
     }
 }
 
diff --git a/lib-nested-core/src/repr_tree/mod.rs b/lib-nested-core/src/repr_tree/mod.rs
index 4ce5391..816f6b7 100644
--- a/lib-nested-core/src/repr_tree/mod.rs
+++ b/lib-nested-core/src/repr_tree/mod.rs
@@ -1,27 +1,50 @@
 pub mod context;
 pub mod morphism;
 
+#[cfg(test)]
+mod tests;
+
 pub use {
     context::{Context},
     morphism::{MorphismType, GenericReprTreeMorphism, MorphismBase}
 };
 
 use {
-    r3vi::view::{AnyOuterViewPort, OuterViewPort, View, singleton::*},
+    r3vi::{
+        view::{
+            ViewPort, OuterViewPort,
+            AnyViewPort, AnyInnerViewPort, AnyOuterViewPort,
+            port::UpdateTask,
+            View,
+            singleton::*, sequence::*
+        },
+        buffer::{singleton::*, vec::*}
+    },
     laddertypes::{TypeTerm},
     std::{
         collections::HashMap,
         sync::{Arc, RwLock},
+        any::Any
     },
 };
 
 //<<<<>>>><<>><><<>><<<*>>><<>><><<>><<<<>>>>
 
 #[derive(Clone)]
-pub struct ReprTree {    
+pub struct ReprLeaf {
+    out_port: AnyViewPort,
+    in_port: AnyInnerViewPort,
+    data: Option< Arc<dyn Any + Send + Sync> >,
+ 
+    /// keepalive for the observer that updates the buffer from in_port
+    keepalive: Option<Arc<dyn Any + Send + Sync>>,
+}
+
+#[derive(Clone)]
+pub struct ReprTree {
     type_tag: TypeTerm,
-    port: Option<AnyOuterViewPort>,
     branches: HashMap<TypeTerm, Arc<RwLock<ReprTree>>>,
+    leaf: Option< ReprLeaf >
 }
 
 //<<<<>>>><<>><><<>><<<*>>><<>><><<>><<<<>>>>
@@ -38,18 +61,282 @@ impl std::fmt::Debug for ReprTree {
     }
 }
 
+//<<<<>>>><<>><><<>><<<*>>><<>><><<>><<<<>>>>
+
+impl ReprLeaf {
+    pub fn from_view<V>( src_port: OuterViewPort<V> ) -> Self
+    where V: View + ?Sized + 'static,
+        V::Msg: Clone
+    {
+        let mut in_port = ViewPort::<V>::new();
+        in_port.attach_to(src_port);
+
+        let mut buf_port = ViewPort::<V>::new();
+        buf_port.attach_to(in_port.outer());
+
+        ReprLeaf {
+            keepalive: None,
+            in_port: in_port.inner().into(),
+            out_port: buf_port.into(),
+            data: None, 
+        }
+    }
+
+    pub fn attach_to<V>(&mut self, src_port: OuterViewPort<V>)
+    where V: View + ?Sized + 'static,
+        V::Msg: Clone
+    {
+        self.in_port.clone()
+            .downcast::<V>().ok().unwrap()
+            .0.attach_to( src_port );
+    }
+
+    pub fn from_singleton_buffer<T>( buffer: SingletonBuffer<T> ) -> Self
+    where T: Clone + Send + Sync + 'static
+    {
+        let in_port = ViewPort::<dyn SingletonView<Item = T>>::new();
+        ReprLeaf {
+            keepalive: Some(buffer.attach_to(in_port.outer())),
+            in_port: in_port.inner().into(),
+            out_port: buffer.get_port().0.into(),
+            data: Some(buffer.into_inner())
+        }
+    }
+
+    pub fn as_singleton_buffer<T>(&mut self) -> Option<SingletonBuffer<T>>
+    where T: Clone + Send + Sync + 'static
+    {
+        let sgl_port = self.get_port::< dyn SingletonView<Item = T> >().unwrap().0;
+
+        let data_arc =
+            if let Some(data) = self.data.as_ref() {
+                data.clone().downcast::<RwLock<T>>().ok()
+            } else {
+                sgl_port.update();
+                let value = sgl_port.outer().get_view().unwrap().get();
+                eprintln!("make new data ARC from old value");
+                Some(Arc::new(RwLock::new( value )))
+            };
+
+        if let Some(data_arc) = data_arc {
+            self.data = Some(data_arc.clone() as Arc<dyn Any + Send + Sync>);
+            let buf = SingletonBuffer {
+                value: data_arc,
+                port: sgl_port.inner()
+            };
+            self.keepalive = Some(buf.attach_to(
+                self.in_port.0.clone()
+                    .downcast::<dyn SingletonView<Item = T>>()
+                    .ok().unwrap()
+                    .outer()
+            ));
+            Some(buf)
+        } else {
+            None
+        }
+    }
+
+    pub fn get_port<V>(&self) -> Option<OuterViewPort<V>>
+    where V: View + ?Sized + 'static,
+        V::Msg: Clone
+    {
+        self.out_port.clone().downcast::<V>().ok().map(|p| p.outer())
+    }
+}
+
+//<<<<>>>><<>><><<>><<<*>>><<>><><<>><<<<>>>>
+
+impl ReprTree {
+    pub fn new(type_tag: impl Into<TypeTerm>) -> Self {
+        ReprTree {
+            type_tag: type_tag.into(),
+            branches: HashMap::new(),
+            leaf: None
+        }
+    }
+
+    pub fn new_arc(type_tag: impl Into<TypeTerm>) -> Arc<RwLock<Self>> {
+        Arc::new(RwLock::new(Self::new(type_tag)))
+    }
+
+    pub fn get_type(&self) -> &TypeTerm {
+        &self.type_tag
+    }
+
+    pub fn insert_branch(&mut self, repr: Arc<RwLock<ReprTree>>) {
+        self.branches.insert(repr.clone().read().unwrap().type_tag.clone(), repr.clone());
+    }
+
+    pub fn from_char(ctx: &Arc<RwLock<Context>>, c: char ) -> Arc<RwLock<Self>> {
+        ReprTree::from_singleton_buffer(
+            Context::parse(ctx, "Char"),
+            SingletonBuffer::new(c)
+        )
+    }
+
+    pub fn from_view<V>( type_tag: impl Into<TypeTerm>, view: OuterViewPort<V> ) -> Arc<RwLock<Self>>
+    where V: View + ?Sized + 'static,
+        V::Msg: Clone
+    {
+        let mut rt = ReprTree::new(type_tag);
+        rt.leaf = Some(ReprLeaf::from_view(view));
+        Arc::new(RwLock::new(rt))
+    }
+
+    pub fn from_singleton_buffer<T>( type_tag: impl Into<TypeTerm>, buf: SingletonBuffer<T> ) -> Arc<RwLock<Self>>
+    where T: Clone + Send + Sync + 'static
+    {
+        let mut rt = ReprTree::new(type_tag);
+        rt.leaf = Some(ReprLeaf::from_singleton_buffer(buf));
+        Arc::new(RwLock::new(rt))
+    }
+
+    /// find, and if necessary, create corresponding path in repr-tree.
+    /// Attach src_port to input of that node
+    pub fn attach_leaf_to<V>(
+        &mut self,
+        mut type_ladder: impl Iterator<Item = TypeTerm>,
+        src_port: OuterViewPort<V>
+    )
+    where V: View + ?Sized + 'static,
+        V::Msg: Clone
+    {
+        if let Some(rung_type) = type_ladder.next() {
+            if let Some(next_repr) = self.branches.get(&rung_type) {
+                next_repr.write().unwrap().attach_leaf_to(type_ladder, src_port);
+            } else {
+                let mut next_repr = ReprTree::new(rung_type.clone());
+                next_repr.attach_leaf_to(type_ladder, src_port);
+                self.insert_branch(Arc::new(RwLock::new(next_repr)));
+            }
+        } else {
+            if let Some(leaf) = self.leaf.as_mut() {
+                leaf.attach_to(src_port);
+            } else {
+                self.leaf = Some(ReprLeaf::from_view(src_port));
+            }
+        }
+    }
+
+    pub fn insert_leaf(
+        &mut self,
+        mut type_ladder: impl Iterator<Item = TypeTerm>,
+        leaf: ReprLeaf
+    ) {
+        if let Some(type_term) = type_ladder.next() {
+            if let Some(next_repr) = self.branches.get(&type_term) {
+                next_repr.write().unwrap().insert_leaf(type_ladder, leaf);
+            } else {
+                let mut next_repr = ReprTree::new(type_term.clone());
+                next_repr.insert_leaf(type_ladder, leaf);
+                self.insert_branch(Arc::new(RwLock::new(next_repr)));
+            }
+        } else {
+            self.leaf = Some(leaf)
+        }
+    }
+
+    //<<<<>>>><<>><><<>><<<*>>><<>><><<>><<<<>>>>
+
+    pub fn descend_one(&self, dst_type: impl Into<TypeTerm>) -> Option<Arc<RwLock<ReprTree>>> {
+        let dst_type = dst_type.into();
+        assert!( dst_type.is_flat() );
+        self.branches.get(&dst_type).cloned()
+    }
+
+    pub fn descend_ladder(rt: &Arc<RwLock<Self>>, mut repr_ladder: impl Iterator<Item = TypeTerm>) -> Option<Arc<RwLock<ReprTree>>> {
+        if let Some(first) = repr_ladder.next() {
+            let rt = rt.read().unwrap();
+            repr_ladder.fold(
+                rt.descend_one(first),
+                |s, t| s?.descend(t))
+        } else {
+            Some(rt.clone())
+        }
+    }
+
+    pub fn descend(rt: &Arc<RwLock<Self>>, dst_type: impl Into<TypeTerm>) -> Option<Arc<RwLock<ReprTree>>> {
+        ReprTree::descend_ladder(rt, dst_type.into().get_lnf_vec().into_iter())
+    }
+
+    pub fn ascend(rt: &Arc<RwLock<Self>>, type_term: impl Into<TypeTerm>) -> Arc<RwLock<ReprTree>> {
+        let mut n = Self::new(type_term);
+        n.insert_branch(rt.clone());
+        Arc::new(RwLock::new(n))
+    }
+
+    //<<<<>>>><<>><><<>><<<*>>><<>><><<>><<<<>>>>
+
+    pub fn singleton_buffer<T: Clone + Send + Sync + 'static>(&mut self) -> Option<SingletonBuffer<T>> {
+        if let Some(leaf) = self.leaf.as_mut() {
+            leaf.as_singleton_buffer::<T>()
+        } else {
+            None
+        }
+    }
+
+/*
+    pub fn vec_buffer<T: Clone + Send + Sync + 'static>(&self) -> Option<VecBuffer<T>> {
+    }
+*/
+
+    //<<<<>>>><<>><><<>><<<*>>><<>><><<>><<<<>>>>
+
+    pub fn get_port<V: View + ?Sized + 'static>(&self) -> Option<OuterViewPort<V>>
+    where
+        V::Msg: Clone,
+    {
+        if let Some(leaf) = self.leaf.as_ref() {
+            leaf.get_port::<V>()
+        } else {
+            None
+        }
+    }
+
+    pub fn get_view<V: View + ?Sized + 'static>(&self) -> Option<Arc<V>>
+    where
+        V::Msg: Clone,
+    {
+        self.get_port::<V>()?
+            .get_view()
+    }
+
+    //<<<<>>>><<>><><<>><<<*>>><<>><><<>><<<<>>>>
+
+    pub fn view_seq<T: 'static>(&self) -> OuterViewPort<dyn SequenceView<Item = T>> {
+        self.get_port::<dyn SequenceView<Item = T>>().expect("no sequence-view available")
+    }
+
+    pub fn view_char(&self) -> OuterViewPort<dyn SingletonView<Item = char>> {
+        self.get_port::<dyn SingletonView<Item = char>>().expect("no char-view available")
+    }
+
+    pub fn view_u8(&self) -> OuterViewPort<dyn SingletonView<Item = u8>> {
+        self.get_port::<dyn SingletonView<Item = u8>>().expect("no u8-view available")
+    }
+
+    pub fn view_u64(&self) -> OuterViewPort<dyn SingletonView<Item = u64>> {
+        self.get_port::<dyn SingletonView<Item = u64>>().expect("no u64-view available")
+    }
+}
+
+
+
+//<<<<>>>><<>><><<>><<<*>>><<>><><<>><<<<>>>>
+
 pub trait ReprTreeExt {
     fn get_type(&self) -> TypeTerm;
 
-    fn insert_leaf(&mut self, type_ladder: impl Iterator<Item = TypeTerm>, port: AnyOuterViewPort);
+    fn insert_leaf(&mut self, type_ladder: impl Into<TypeTerm>, leaf: ReprLeaf);
     fn insert_branch(&mut self, repr: Arc<RwLock<ReprTree>>);
-    
     fn descend(&self, target_type: impl Into<TypeTerm>) -> Option<Arc<RwLock<ReprTree>>>;
-    fn descend_ladder(&self, ladder: impl Iterator<Item = TypeTerm>) -> Option<Arc<RwLock<ReprTree>>>;
 
     fn view_char(&self) -> OuterViewPort<dyn SingletonView<Item = char>>;
     fn view_u8(&self) -> OuterViewPort<dyn SingletonView<Item = u8>>;
     fn view_u64(&self) -> OuterViewPort<dyn SingletonView<Item = u64>>;
+
+    fn singleton_buffer<T: Clone + Send + Sync + 'static>(&self) -> SingletonBuffer<T>;
+//    fn vec_buffer<T: Clone + Send + Sync + 'static>(&self) -> VecBuffer<T>;
 }
 
 impl ReprTreeExt for Arc<RwLock<ReprTree>> {
@@ -57,8 +344,8 @@ impl ReprTreeExt for Arc<RwLock<ReprTree>> {
         self.read().unwrap().get_type().clone()
     }
 
-    fn insert_leaf(&mut self, type_ladder: impl Iterator<Item = TypeTerm>, port: AnyOuterViewPort) {
-        self.write().unwrap().insert_leaf(type_ladder, port)
+    fn insert_leaf(&mut self, type_ladder: impl Into<TypeTerm>, leaf: ReprLeaf) {
+        self.write().unwrap().insert_leaf(type_ladder.into().get_lnf_vec().into_iter(), leaf)
     }
 
     fn insert_branch(&mut self, repr: Arc<RwLock<ReprTree>>) {
@@ -66,11 +353,7 @@ impl ReprTreeExt for Arc<RwLock<ReprTree>> {
     }
 
     fn descend(&self, target_type: impl Into<TypeTerm>) -> Option<Arc<RwLock<ReprTree>>> {
-        self.read().unwrap().descend(target_type)
-    }
-
-    fn descend_ladder(&self, ladder: impl Iterator<Item = TypeTerm>) -> Option<Arc<RwLock<ReprTree>>> {
-        ReprTree::descend_ladder(self, ladder)
+        ReprTree::descend( self, target_type )
     }
 
     fn view_char(&self) -> OuterViewPort<dyn SingletonView<Item = char>> {
@@ -84,125 +367,16 @@ impl ReprTreeExt for Arc<RwLock<ReprTree>> {
     fn view_u64(&self) -> OuterViewPort<dyn SingletonView<Item = u64>> {
         self.read().unwrap().view_u64()
     }
+
+    fn singleton_buffer<T: Clone + Send + Sync + 'static>(&self) -> SingletonBuffer<T> {
+        self.write().unwrap().singleton_buffer::<T>().expect("")
+    }
+/*
+    fn vec_buffer<T: Clone + Send + Sync + 'static>(&self) -> VecBuffer<T> {
+        self.read().unwrap().vec_buffer::<T>().expect("")
+    }
+    */
 }
 
 //<<<<>>>><<>><><<>><<<*>>><<>><><<>><<<<>>>>
 
-impl ReprTree {
-    pub fn new(type_tag: impl Into<TypeTerm>) -> Self {
-        ReprTree {
-            type_tag: type_tag.into(),
-            port: None,
-            branches: HashMap::new(),
-        }
-    }
-
-    pub fn new_arc(type_tag: impl Into<TypeTerm>) -> Arc<RwLock<Self>> {
-        Arc::new(RwLock::new(Self::new(type_tag)))
-    }
-
-    pub fn get_type(&self) -> &TypeTerm {
-        &self.type_tag
-    }
-
-    pub fn from_char(ctx: &Arc<RwLock<Context>>, c: char) -> Arc<RwLock<Self>> {
-        let buf = r3vi::buffer::singleton::SingletonBuffer::<char>::new(c);
-        ReprTree::new_leaf(
-            Context::parse(ctx, "Char"),
-            buf.get_port().into()
-        )
-    }
-
-    pub fn from_u64(ctx: &Arc<RwLock<Context>>, v: u64) -> Arc<RwLock<Self>> {
-        let buf = r3vi::buffer::singleton::SingletonBuffer::<u64>::new(v);
-        ReprTree::new_leaf(
-            Context::parse(ctx, "<MachineInt 64>"),
-            buf.get_port().into()
-        )
-    }
-
-    pub fn new_leaf(type_tag: impl Into<TypeTerm>, port: AnyOuterViewPort) -> Arc<RwLock<Self>> {
-        let mut tree = ReprTree::new(type_tag.into());
-        tree.insert_leaf(vec![].into_iter(), port);
-        Arc::new(RwLock::new(tree))
-    }
-
-    pub fn insert_branch(&mut self, repr: Arc<RwLock<ReprTree>>) {
-        self.branches.insert(repr.clone().read().unwrap().type_tag.clone(), repr.clone());
-    }
-
-    pub fn insert_leaf(
-        &mut self,
-        mut type_ladder: impl Iterator<Item = TypeTerm>,
-        port: AnyOuterViewPort,
-    ) {
-        if let Some(type_term) = type_ladder.next() {
-            if let Some(next_repr) = self.branches.get(&type_term) {
-                next_repr.write().unwrap().insert_leaf(type_ladder, port);
-            } else {
-                let mut next_repr = ReprTree::new(type_term.clone());
-                next_repr.insert_leaf(type_ladder, port);
-                self.insert_branch(Arc::new(RwLock::new(next_repr)));
-            }
-        } else {
-            self.port = Some(port);
-        }
-    }
-
-    //<<<<>>>><<>><><<>><<<*>>><<>><><<>><<<<>>>>
-
-
-    pub fn view_char(&self) -> OuterViewPort<dyn SingletonView<Item = char>> {
-        self.get_port::<dyn SingletonView<Item = char>>().expect("no char-view available")
-    }
-
-    pub fn view_u8(&self) -> OuterViewPort<dyn SingletonView<Item = u8>> {
-        self.get_port::<dyn SingletonView<Item = u8>>().expect("no u8-view available")
-    }
-
-    pub fn view_u64(&self) -> OuterViewPort<dyn SingletonView<Item = u64>> {
-        self.get_port::<dyn SingletonView<Item = u64>>().expect("no u64-view available")
-    }
-
-    pub fn get_port<V: View + ?Sized + 'static>(&self) -> Option<OuterViewPort<V>>
-    where
-        V::Msg: Clone,
-    {
-        Some(
-            self.port
-                .clone()?
-                .downcast::<V>()
-                .ok()?
-        )
-    }
-
-    pub fn get_view<V: View + ?Sized + 'static>(&self) -> Option<Arc<V>>
-    where
-        V::Msg: Clone,
-    {
-            self.get_port::<V>()?
-                .get_view()
-    }
-
-    pub fn descend(&self, dst_type: impl Into<TypeTerm>) -> Option<Arc<RwLock<ReprTree>>> {
-        self.branches.get(&dst_type.into()).cloned()
-    }
-
-    pub fn descend_ladder(rt: &Arc<RwLock<Self>>, mut repr_ladder: impl Iterator<Item = TypeTerm>) -> Option<Arc<RwLock<ReprTree>>> {
-        if let Some(first) = repr_ladder.next() {
-            let rt = rt.read().unwrap();
-            repr_ladder.fold(
-                rt.descend(first),
-                |s, t| s?.read().unwrap().descend(t))
-        } else {
-            Some(rt.clone())
-        }
-    }
-
-    pub fn ascend(rt: &Arc<RwLock<Self>>, type_term: impl Into<TypeTerm>) -> Arc<RwLock<ReprTree>> {
-        let mut n = Self::new(type_term);
-        n.insert_branch(rt.clone());
-        Arc::new(RwLock::new(n))
-    }
-}
-
diff --git a/lib-nested-core/src/repr_tree/morphism.rs b/lib-nested-core/src/repr_tree/morphism.rs
index 689cffc..64ea186 100644
--- a/lib-nested-core/src/repr_tree/morphism.rs
+++ b/lib-nested-core/src/repr_tree/morphism.rs
@@ -1,7 +1,8 @@
 use {
     laddertypes::{TypeTerm, TypeID},
+    r3vi::view::AnyOuterViewPort,
     crate::{
-        repr_tree::{ReprTree},
+        repr_tree::{ReprTree, ReprTreeExt, ReprLeaf},
     },
     std::{
         sync::{Arc, RwLock},
@@ -20,8 +21,9 @@ pub struct MorphismType {
 #[derive(Clone)]
 pub struct GenericReprTreeMorphism {
     morph_type: MorphismType,
-    repr_tree_op: Arc<
-        dyn Fn( Arc<RwLock<ReprTree>>, &HashMap<TypeID, TypeTerm> )
+    setup_projection: Arc<
+        dyn Fn( &mut Arc<RwLock<ReprTree>>, &HashMap<TypeID, TypeTerm> )
+//            -> Result< ReprLeaf, () >
         + Send + Sync
     >
 }
@@ -43,12 +45,15 @@ impl MorphismBase {
     pub fn add_morphism(
         &mut self,
         morph_type: MorphismType,
-        repr_tree_op: impl Fn( Arc<RwLock<ReprTree>>, &HashMap<TypeID, TypeTerm> ) + Send + Sync + 'static
+        setup_projection:
+            impl Fn( &mut Arc<RwLock<ReprTree>>, &HashMap<TypeID, TypeTerm> )
+//                -> Result< ReprLeaf, () /* TODO: error */ >
+            + Send + Sync + 'static
     ) {
         self.morphisms.push(
             GenericReprTreeMorphism {
                 morph_type,
-                repr_tree_op: Arc::new(repr_tree_op)
+                setup_projection: Arc::new(setup_projection)
             }
         );
     }
@@ -75,14 +80,15 @@ impl MorphismBase {
         None
     }
 
-    pub fn morph(
+    pub fn apply_morphism(
         &self,
-        repr_tree: Arc<RwLock<ReprTree>>,
-        target_type: &TypeTerm
+        mut repr_tree: Arc<RwLock<ReprTree>>,
+        src_type: &TypeTerm,
+        dst_type: &TypeTerm
     ) {
-        let t = repr_tree.read().unwrap().get_type().clone();
-        if let Some((m, σ)) = self.find_morphism( &t, target_type ) {
-            (m.repr_tree_op)( repr_tree.clone(), &σ );
+//        let t = repr_tree.read().unwrap().get_type().clone();
+        if let Some((m, σ)) = self.find_morphism( &src_type, dst_type ) {
+            (m.setup_projection)( &mut repr_tree, &σ );
         } else {
             eprintln!("could not find morphism");
         }
diff --git a/lib-nested-core/src/repr_tree/tests.rs b/lib-nested-core/src/repr_tree/tests.rs
new file mode 100644
index 0000000..19fa23c
--- /dev/null
+++ b/lib-nested-core/src/repr_tree/tests.rs
@@ -0,0 +1,168 @@
+
+use {
+    r3vi::{
+        buffer::singleton::{
+            SingletonBuffer
+        },
+        view::port::UpdateTask
+    },
+    crate::{
+        repr_tree::{Context, ReprTreeExt, ReprTree, ReprLeaf}
+    },
+    std::sync::{Arc, RwLock}
+};
+
+#[test]
+fn char_view() {
+    let ctx = Arc::new(RwLock::new(Context::new()));
+    crate::editors::digit::init_ctx( ctx.clone() );
+
+    let mut rt_digit = ReprTree::new_arc( Context::parse(&ctx, "<Digit 16>") );
+    rt_digit.insert_leaf(
+        Context::parse(&ctx, "Char"),
+        ReprLeaf::from_singleton_buffer( SingletonBuffer::new('5') )
+    );
+
+    //<><><><>
+    let mut digit_char_buffer = rt_digit
+        .descend( Context::parse(&ctx, "Char") ).unwrap()
+        .singleton_buffer::<char>();
+
+    assert_eq!( digit_char_buffer.get(), '5' );
+    //<><><><>
+
+    let digit_char_view = rt_digit
+        .descend(Context::parse(&ctx, "Char")).unwrap()
+        .view_char();
+
+    assert_eq!( digit_char_view.get_view().unwrap().get(), '5' );
+
+
+    //<><><><>
+    // `Char-view` is correctly coupled to `char-buffer`
+    digit_char_buffer.set('2');
+    assert_eq!( digit_char_view.get_view().unwrap().get(), '2' );
+}
+
+#[test]
+fn digit_projection_char_to_u8() {
+    let ctx = Arc::new(RwLock::new(Context::new()));
+    crate::editors::digit::init_ctx( ctx.clone() );
+
+    let mut rt_digit = ReprTree::new_arc( Context::parse(&ctx, "<Digit 16>") );
+
+    rt_digit.insert_leaf(
+        Context::parse(&ctx, "Char"),
+        ReprLeaf::from_singleton_buffer( SingletonBuffer::new('5') )
+    );
+
+    //<><><><>
+    // add another representation
+ 
+    ctx.read().unwrap().morphisms.apply_morphism(
+        rt_digit.clone(),
+        &Context::parse(&ctx, "<Digit 16>~Char"),
+        &Context::parse(&ctx, "<Digit 16>~ℤ_256~machine::UInt8")
+    );
+
+    let digit_u8_view = rt_digit
+        .descend(Context::parse(&ctx, "ℤ_256~machine::UInt8")).unwrap()
+        .view_u8();
+
+    assert_eq!( digit_u8_view.get_view().unwrap().get(), 5 as u8 );
+
+
+    // projection behaves accordingly , when buffer is changed
+
+    let mut digit_char_buffer = rt_digit
+        .descend( Context::parse(&ctx, "Char") ).unwrap()
+        .singleton_buffer::<char>();
+
+    digit_char_buffer.set('2');
+    assert_eq!( digit_u8_view.get_view().unwrap().get(), 2 as u8 );
+}
+
+#[test]
+fn digit_projection_u8_to_char() {
+    let ctx = Arc::new(RwLock::new(Context::new()));
+    crate::editors::digit::init_ctx( ctx.clone() );
+
+    let mut rt_digit = ReprTree::new_arc( Context::parse(&ctx, "<Digit 16>") );
+
+    rt_digit.insert_leaf(
+        Context::parse(&ctx, "ℤ_256~machine::UInt8"),
+        ReprLeaf::from_singleton_buffer( SingletonBuffer::new(5 as u8) )
+    );
+
+    //<><><><>
+    // add another representation
+ 
+    ctx.read().unwrap().morphisms.apply_morphism(
+        rt_digit.clone(),
+        &Context::parse(&ctx, "<Digit 16>~ℤ_256~machine::UInt8"),
+        &Context::parse(&ctx, "<Digit 16>~Char")
+    );
+
+    let digit_u8_view = rt_digit
+        .descend(Context::parse(&ctx, "Char")).unwrap()
+        .view_char();
+
+    assert_eq!( digit_u8_view.get_view().unwrap().get(), '5' );
+}
+
+
+#[test]
+fn char_buffered_projection() {
+    let ctx = Arc::new(RwLock::new(Context::new()));
+    crate::editors::digit::init_ctx( ctx.clone() );
+
+    let mut rt_digit = ReprTree::new_arc( Context::parse(&ctx, "<Digit 16>") );
+
+    rt_digit.insert_leaf(
+        Context::parse(&ctx, "ℤ_256~machine::UInt8"),
+        ReprLeaf::from_singleton_buffer( SingletonBuffer::new(8 as u8) )
+    );
+
+    let mut digit_u8_buffer = rt_digit
+        .descend(Context::parse(&ctx, "ℤ_256~machine::UInt8")).unwrap()
+        .singleton_buffer::<u8>();
+
+    assert_eq!( digit_u8_buffer.get(), 8 );
+
+    rt_digit.insert_leaf(
+        Context::parse(&ctx, "Char"),
+        ReprLeaf::from_singleton_buffer( SingletonBuffer::new('5') )
+    );
+
+    let digit_char_buf = rt_digit
+        .descend(Context::parse(&ctx, "Char")).unwrap()
+        .singleton_buffer::<char>();
+    let digit_char_view = rt_digit
+        .descend(Context::parse(&ctx, "Char")).unwrap()
+        .view_char();
+
+    // before setting up the morphism, char-view remains as initialized
+    assert_eq!( digit_char_buf.get(), '5' );
+    assert_eq!( digit_char_view.get_view().unwrap().get(), '5' );
+
+    // now we attach the char-repr to the u8-repr
+    ctx.read().unwrap().morphisms.apply_morphism(
+        rt_digit.clone(),
+        &Context::parse(&ctx, "<Digit 16>~ℤ_256~machine::UInt8"),
+        &Context::parse(&ctx, "<Digit 16>~Char")
+    );
+
+    // char buffer and view should now follow the u8-buffer
+    assert_eq!( digit_char_view.get_view().unwrap().get(), '8' );
+    assert_eq!( digit_char_buf.get(), '8' );
+
+    // now u8-buffer changes, and char-buffer should change accordingly
+    digit_u8_buffer.set(3);
+    assert_eq!( digit_u8_buffer.get(), 3 );
+
+    // char buffer should follow
+    digit_char_view.0.update();
+    assert_eq!( digit_char_buf.get(), '3' );
+    assert_eq!( digit_char_view.get_view().unwrap().get(), '3' ); 
+}
+
diff --git a/lib-nested-tty/src/edit_tree/keymap.rs b/lib-nested-tty/src/edit_tree/keymap.rs
index 1afc123..09a3609 100644
--- a/lib-nested-tty/src/edit_tree/keymap.rs
+++ b/lib-nested-tty/src/edit_tree/keymap.rs
@@ -68,20 +68,20 @@ impl TerminalEvent {
         match self {
             TerminalEvent::Input(Event::Key(key)) => {
                 if let Some(tree_nav_cmd) = neo2_treenav_keymap(key) {
-                    ReprTree::new_leaf(
+                    ReprTree::from_singleton_buffer(
                         Context::parse(&ctx, "TreeNavCmd"),
-                        SingletonBuffer::new(tree_nav_cmd).get_port().into()
+                        SingletonBuffer::new(tree_nav_cmd)
                     )
                 } else if let Some(tree_nav_cmd) = universal_treenav_keymap(key) {
-                    ReprTree::new_leaf(
+                    ReprTree::from_singleton_buffer(
                         Context::parse(&ctx, "TreeNavCmd"),
-                        SingletonBuffer::new(tree_nav_cmd).get_port().into()
+                        SingletonBuffer::new(tree_nav_cmd)
                     )
                 } else {
                     if let Some(list_cmd) = tty_list_keymap(key) {
-                        ReprTree::new_leaf(
+                        ReprTree::from_singleton_buffer(
                             Context::parse(&ctx, "ListCmd"),
-                            SingletonBuffer::new(list_cmd).get_port().into()
+                            SingletonBuffer::new(list_cmd)
                         )
                     } else {
                         match key {
@@ -89,9 +89,9 @@ impl TerminalEvent {
                                 ReprTree::from_char(&ctx, *c)
                             }
                             _ => {
-                                ReprTree::new_leaf(
+                                ReprTree::from_singleton_buffer(
                                     Context::parse(&ctx, "TerminalEvent"),
-                                    SingletonBuffer::new(self.clone()).get_port().into()
+                                    SingletonBuffer::new(self.clone())
                                 )
                             }
                         }
@@ -99,9 +99,9 @@ impl TerminalEvent {
                 }
             }
             _ => {
-                ReprTree::new_leaf(
+                ReprTree::from_singleton_buffer(
                     Context::parse(&ctx, "TerminalEvent"),
-                    SingletonBuffer::new(self.clone()).get_port().into()
+                    SingletonBuffer::new(self.clone())
                 )
             }
         }
diff --git a/lib-nested-tty/src/editors/list.rs b/lib-nested-tty/src/editors/list.rs
index 3affc68..b3ce8a9 100644
--- a/lib-nested-tty/src/editors/list.rs
+++ b/lib-nested-tty/src/editors/list.rs
@@ -94,12 +94,12 @@ impl PTYListStyle {
     pub fn for_node(node: &mut EditTree, style: (&str, &str, &str)) {
         node.disp.view
             .write().unwrap()
-            .insert_branch(ReprTree::new_leaf(
+            .insert_branch(ReprTree::from_view(
                 Context::parse(&node.ctx, "TerminalView"),
                 Self::new(style)
                     .pty_view(
                         &node.get_edit::<ListEditor>().unwrap().read().unwrap()
-                ).into()
+                )
             ));
     }
 }
@@ -225,6 +225,7 @@ impl PTYListController {
                     rt,
                     self.depth.map(|d| d+1)
                 );
+                /*
                 let mut ne = new_edittree.write().unwrap();
                 match ne.send_cmd_obj(cmd_obj.clone()) {
                     TreeNavResult::Continue => {
@@ -233,9 +234,12 @@ impl PTYListController {
                         TreeNavResult::Continue
                     }
                     TreeNavResult::Exit => {
+                */
                         TreeNavResult::Exit
+            /*
                     }
                 }
+                */
             },
             ListCursorMode::Select => {
                 if let Some(item) = e.get_item_mut() {
diff --git a/lib-nested-tty/src/editors/mod.rs b/lib-nested-tty/src/editors/mod.rs
index 8194268..4ce366e 100644
--- a/lib-nested-tty/src/editors/mod.rs
+++ b/lib-nested-tty/src/editors/mod.rs
@@ -17,12 +17,14 @@ use {
     }
 };
 
+
 pub fn edittree_make_char_view(
     node: EditTree
 ) -> EditTree {
+    eprintln!("nested-tty: EditTree make char-view");
     node.disp.view
         .write().unwrap()
-        .insert_branch(ReprTree::new_leaf(
+        .insert_branch(ReprTree::from_view(
             Context::parse(&node.ctx, "TerminalView"),
             node.get_edit::< nested::editors::char::CharEditor >()
                 .unwrap()
@@ -31,7 +33,6 @@ pub fn edittree_make_char_view(
                 .get_port()
                 .map(move |c| TerminalAtom::from(if c == '\0' { ' ' } else { c }))
                 .to_grid()
-                .into(),
         ));
 
     node
@@ -42,7 +43,7 @@ pub fn edittree_make_digit_view(
 ) -> EditTree {
     node.disp.view
         .write().unwrap()
-        .insert_branch(ReprTree::new_leaf(
+        .insert_branch(ReprTree::from_view(
             Context::parse(&node.ctx, "TerminalView"),
             node.get_edit::< nested::editors::digit::DigitEditor >()
                 .unwrap()
@@ -56,7 +57,6 @@ pub fn edittree_make_digit_view(
                     }
                 )
                 .to_grid()
-                .into(),
         ));
 
     node
diff --git a/lib-nested-tty/src/lib.rs b/lib-nested-tty/src/lib.rs
index f5631af..0da7946 100644
--- a/lib-nested-tty/src/lib.rs
+++ b/lib-nested-tty/src/lib.rs
@@ -39,13 +39,12 @@ pub trait DisplaySegment {
 }
 
 
-use nested::repr_tree::Context;
+use nested::repr_tree::{Context, ReprTreeExt};
 use std::sync::{Arc, RwLock};
 
 impl DisplaySegment for nested::edit_tree::EditTree {
     fn display_view(&self) -> OuterViewPort<dyn TerminalView> {
         if let Some( tv_repr ) = self.disp.view
-            .read().unwrap()
             .descend( Context::parse(&self.ctx, "TerminalView") )
         {
             if let Some(port) =