diff --git a/Cargo.toml b/Cargo.toml
index 73f07fc..b3de67d 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -5,5 +5,6 @@ members = [
     "examples/tty-01-hello",
     "examples/tty-02-digit",
     "examples/tty-03-string",
+    "examples/tty-04-posint"
 ]
 
diff --git a/examples/tty-04-posint/Cargo.toml b/examples/tty-04-posint/Cargo.toml
new file mode 100644
index 0000000..0e4e285
--- /dev/null
+++ b/examples/tty-04-posint/Cargo.toml
@@ -0,0 +1,19 @@
+[package]
+name = "tty-04-posint"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+laddertypes = { path = "../../../lib-laddertypes" }
+r3vi = { path = "../../../lib-r3vi" }
+nested = { path = "../../lib-nested-core" }
+nested-tty = { path = "../../lib-nested-tty" }
+termion = "*"
+cgmath = "*"
+
+[dependencies.async-std]
+version = "1.9.0"
+features = ["unstable", "attributes"]
+
diff --git a/examples/tty-04-posint/README.md b/examples/tty-04-posint/README.md
new file mode 100644
index 0000000..1f85cdd
--- /dev/null
+++ b/examples/tty-04-posint/README.md
@@ -0,0 +1,7 @@
+# tty-04-posint
+
+In the following example, a <List Char> editor
+as before is used, but its data is morphed into
+representing a positional integer which is then
+projected into different radices and displayed
+in different views on screen
diff --git a/examples/tty-04-posint/src/main.rs b/examples/tty-04-posint/src/main.rs
new file mode 100644
index 0000000..687d345
--- /dev/null
+++ b/examples/tty-04-posint/src/main.rs
@@ -0,0 +1,208 @@
+//! In the following example, a <List Char> editor
+//! as before is used, but its data is morphed into
+//! representing a positional integer which is then
+//! projected into different radices and displayed
+//! in different views on screen
+
+extern crate cgmath;
+extern crate nested;
+extern crate nested_tty;
+extern crate r3vi;
+extern crate termion;
+
+use {
+    cgmath::Vector2,
+    nested::{
+        editors::{
+            ObjCommander
+        },
+        repr_tree::{Context, ReprTree, ReprTreeExt, ReprLeaf},
+        edit_tree::{EditTree}
+    },
+    nested_tty::{
+        DisplaySegment, TTYApplication,
+        TerminalCompositor, TerminalStyle, TerminalView,
+        TerminalAtom, TerminalEvent
+    },
+    r3vi::{
+        buffer::{singleton::*, vec::*},
+        view::{port::UpdateTask, list::*, sequence::*},
+        projection::*
+    },
+    std::sync::{Arc, RwLock},
+};
+
+#[async_std::main]
+async fn main() {
+    /* setup context
+     */
+    let ctx = Arc::new(RwLock::new(Context::new()));
+    nested::editors::char::init_ctx( ctx.clone() );
+    nested::editors::digit::init_ctx( ctx.clone() );
+    nested::editors::integer::init_ctx( ctx.clone() );
+    nested::editors::list::init_ctx( ctx.clone() );
+    nested_tty::setup_edittree_hook(&ctx);
+
+    /* Create a Representation-Tree of type <List <Digit 16>>
+     */
+    let mut rt_digitlist = ReprTree::new_arc( Context::parse(&ctx, "<List <Digit 16>>") );
+    let mut rt_digitseq = ReprTree::new_arc( Context::parse(&ctx, "<Seq <Digit 16>>") );
+    rt_digitseq.insert_branch( rt_digitlist );
+    let mut rt_posint = ReprTree::new_arc(Context::parse(&ctx, "<PosInt 16 BigEndian>"));
+    rt_posint.insert_branch( rt_digitseq );
+    let mut rt_int = ReprTree::new_arc( Context::parse(&ctx, "ℕ") );
+    rt_int.insert_branch( rt_posint );
+
+    /* Setup an Editor for this ReprTree
+     * (this will add the representation <List <Digit 16>>~EditTree to the ReprTree)
+     */
+    let rt_edittree_list = ctx.read().unwrap()
+        .setup_edittree(
+            ReprTree::descend(
+                &rt_int,
+                Context::parse(&ctx, "<PosInt 16 BigEndian>~<Seq~List <Digit 16>>")
+            ).expect("cant descend reprtree"),
+            SingletonBuffer::new(0).get_port()
+        );
+
+    ctx.read().unwrap().morphisms.apply_morphism(
+        ReprTree::descend(&rt_int,
+            Context::parse(&ctx, "
+                    <PosInt 16 BigEndian>
+                    ~<Seq <Digit 16>>
+                    ~<List <Digit 16>>
+                ")
+        ).expect("cant descend repr tree"),
+        &Context::parse(&ctx, "<List <Digit 16>>~EditTree"),
+        &Context::parse(&ctx, "<List <Digit 16>~Char>")
+    );
+
+    /*
+     * map seq of chars to seq of u64 digits
+     */
+    let mut chars_view =
+        ReprTree::descend(
+            &rt_int,
+            Context::parse(&ctx, "<PosInt 16 BigEndian>~<Seq <Digit 16>>~<List <Digit 16>~Char>")
+        ).expect("cant descend")
+        .read().unwrap()
+        .get_port::<dyn ListView<char>>()
+        .unwrap();
+
+    let mut digits_view = chars_view
+        .to_sequence()
+        .filter_map(
+            |digit_char|
+
+            /* TODO: call morphism
+             */
+            match digit_char.to_digit(16) {
+                Some(d) => Some(d as usize),
+                None    => None
+            }
+        );
+
+    rt_int.write().unwrap().insert_leaf(
+        vec![
+            Context::parse(&ctx, "<PosInt 16 BigEndian>"),
+            Context::parse(&ctx, "<Seq <Digit 16>>"),
+            Context::parse(&ctx, "<Seq ℤ_2^64>"),
+            Context::parse(&ctx, "<Seq machine.UInt64>")
+        ].into_iter(),
+        nested::repr_tree::ReprLeaf::from_view( digits_view.clone() )
+    );
+    //
+    //
+
+    ctx.read().unwrap().morphisms.apply_morphism(
+        rt_int.clone(),
+        &Context::parse(&ctx, "ℕ ~ <PosInt 16 BigEndian> ~ <Seq <Digit 16>~ℤ_2^64~machine.UInt64>"),
+        &Context::parse(&ctx, "ℕ ~ <PosInt 16 LittleEndian> ~ <Seq <Digit 16>~ℤ_2^64~machine.UInt64>")
+    );
+    ctx.read().unwrap().morphisms.apply_morphism(
+        rt_int.clone(),
+        &Context::parse(&ctx, "ℕ ~ <PosInt 16 LittleEndian> ~ <Seq <Digit 16>~ℤ_2^64~machine.UInt64>"),
+        &Context::parse(&ctx, "ℕ ~ <PosInt 10 LittleEndian> ~ <Seq <Digit 10>~ℤ_2^64~machine.UInt64>")
+    );
+    ctx.read().unwrap().morphisms.apply_morphism(
+        rt_int.clone(),
+        &Context::parse(&ctx, "ℕ ~ <PosInt 10 LittleEndian> ~ <Seq <Digit 10>~ℤ_2^64~machine.UInt64>"),
+        &Context::parse(&ctx, "ℕ ~ <PosInt 10 BigEndian> ~ <Seq <Digit 10>~ℤ_2^64~machine.UInt64>")
+    );
+
+    let dec_digits_view = ReprTree::descend(&rt_int,
+        Context::parse(&ctx, "
+                <PosInt 10 BigEndian>
+                ~< Seq <Digit 10>~ℤ_2^64~machine.UInt64 >
+        ")
+    ).expect("cant descend repr tree")
+        .read().unwrap()
+        .get_port::<dyn SequenceView<Item = usize>>().unwrap()
+        .map(
+            /* TODO: call morphism
+             */
+            |digit| {
+                TerminalAtom::from(
+                    char::from_digit(*digit as u32, 10)
+                )
+            }
+        )
+        .to_grid_horizontal();
+
+    let hex_digits_view =
+        ReprTree::descend(
+            &rt_int,
+            Context::parse(&ctx, "
+                <PosInt 16 BigEndian>
+                ~<Seq  <Digit 16>  >
+                ~<List <Digit 16>
+                       ~Char>")
+        ).expect("cant descend")
+        .read().unwrap()
+        .get_port::<dyn ListView<char>>().unwrap()
+        .to_sequence()
+        .to_grid_horizontal()
+        .map_item(|_pt,c| TerminalAtom::new(*c, TerminalStyle::fg_color((30,90,200))));
+
+    /* setup terminal
+     */
+    let app = TTYApplication::new({
+        let edittree_list = rt_edittree_list.clone();
+
+        /* event handler
+         */
+        let ctx = ctx.clone();
+        move |ev| {
+            edittree_list.get().send_cmd_obj(ev.to_repr_tree(&ctx));
+        }
+    });
+
+    /* Setup the compositor to serve as root-view
+     * by routing it to the `app.port` Viewport,
+     * so it will be displayed on TTY-output.
+     */
+    let compositor = TerminalCompositor::new(app.port.inner());
+
+    /* Now add some views to our compositor
+     */
+    {
+        let mut comp = compositor.write().unwrap();
+
+        let label_str = ctx.read().unwrap().type_term_to_str(&rt_int.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(1,1)));
+
+        comp.push(rt_edittree_list.get()
+                .display_view()
+                .offset(Vector2::new(3,2)));
+
+        comp.push(dec_digits_view.offset(Vector2::new(3,4)));
+        comp.push(hex_digits_view.offset(Vector2::new(3,5)));
+    }
+
+    /* write the changes in the view of `term_port` to the terminal
+     */
+    app.show().await.expect("output error!");
+}
diff --git a/lib-nested-core/src/editors/char/mod.rs b/lib-nested-core/src/editors/char/mod.rs
index 079fa85..b4d0e51 100644
--- a/lib-nested-core/src/editors/char/mod.rs
+++ b/lib-nested-core/src/editors/char/mod.rs
@@ -36,6 +36,7 @@ pub fn init_ctx( ctx: Arc<RwLock<Context>> ) {
                         if let Some(buf) = rt.singleton_buffer::<char>() {
                             // buffer already exists
                         } else {
+                            // create char buffer
                             rt.insert_leaf(
                                 vec![].into_iter(),
                                 ReprLeaf::from_singleton_buffer(
diff --git a/lib-nested-core/src/editors/digit/ctx.rs b/lib-nested-core/src/editors/digit/ctx.rs
index 8547552..d5822c2 100644
--- a/lib-nested-core/src/editors/digit/ctx.rs
+++ b/lib-nested-core/src/editors/digit/ctx.rs
@@ -80,7 +80,7 @@ pub fn init_ctx( ctx: Arc<RwLock<Context>> ) {
     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")
+                dst_type: Context::parse(&ctx, "<Digit Radix>~ℤ_2^64~machine.UInt64")
             };
 
     ctx.write().unwrap()
@@ -124,7 +124,7 @@ pub fn init_ctx( ctx: Arc<RwLock<Context>> ) {
 
     let morphtype =
             crate::repr_tree::MorphismType {
-                src_type: Context::parse(&ctx, "<Digit Radix>~ℤ_256~machine::UInt8"),
+                src_type: Context::parse(&ctx, "<Digit Radix>~ℤ_2^64~machine.UInt64"),
                 dst_type: Context::parse(&ctx, "<Digit Radix>~Char")
             };
 
@@ -144,10 +144,10 @@ pub fn init_ctx( ctx: Arc<RwLock<Context>> ) {
                     /* insert projected view into ReprTree
                      */
                     let char_view = 
-                        rt.descend(Context::parse(&ctx, "ℤ_256~machine::UInt8"))
+                        rt.descend(Context::parse(&ctx, "ℤ_2^64~machine::UInt64"))
                             .unwrap()
-                            .view_u8()
-                            .map(move |digit| char::from_digit(digit as u32, radix).unwrap_or('?'));
+                            .view_usize()
+                            .map(move |digit| char::from_digit((digit%radix as usize) as u32, radix).unwrap_or('?'));
 
                     rt.write().unwrap().attach_leaf_to::<dyn SingletonView<Item = char>>(
                         Context::parse(&ctx, "Char").get_lnf_vec().into_iter(),
diff --git a/lib-nested-core/src/editors/digit/editor.rs b/lib-nested-core/src/editors/digit/editor.rs
index a73733b..125d2a3 100644
--- a/lib-nested-core/src/editors/digit/editor.rs
+++ b/lib-nested-core/src/editors/digit/editor.rs
@@ -73,6 +73,11 @@ impl DigitEditor {
     pub fn get_type(&self) -> TypeTerm {
         TypeTerm::TypeID(self.ctx.read().unwrap().get_typeid("Digit").unwrap())
     }
+
+    pub fn get_char(&self) -> char {
+        self.data.get()
+    }
+
 /*
     pub fn get_data(&self) -> Arc<RwLock<ReprTree>> {
         ReprTree::ascend(
diff --git a/lib-nested-core/src/editors/integer/ctx.rs b/lib-nested-core/src/editors/integer/ctx.rs
index b8bfac2..23eeab6 100644
--- a/lib-nested-core/src/editors/integer/ctx.rs
+++ b/lib-nested-core/src/editors/integer/ctx.rs
@@ -5,8 +5,7 @@ use {
     },
     laddertypes::{TypeTerm},
     crate::{
-        repr_tree::{Context},
-        repr_tree::{MorphismType},
+        repr_tree::{ReprTree, ReprLeaf, Context, MorphismType},
         editors::{
             list::*,
             integer::*
@@ -16,97 +15,142 @@ use {
 };
 
 pub fn init_ctx(ctx: Arc<RwLock<Context>>) {
-    /*
-    ctx.add_list_typename("PosInt".into());
-    let pattern = MorphismTypePattern {
-        src_tyid: ctx.get_typeid("List"),
-        dst_tyid: ctx.get_typeid("PosInt").unwrap()
+    // TODO: proper scoping
+    // ctx.write().unwrap().add_varname("Radix");
+    ctx.write().unwrap().add_varname("SrcRadix");
+    ctx.write().unwrap().add_varname("DstRadix");
+
+    let morphism_type = MorphismType {
+        src_type: Context::parse(&ctx, "ℕ ~ <PosInt Radix BigEndian> ~ <Seq <Digit SrcRadix>~ℤ_2^64~machine.UInt64>"),
+        dst_type: Context::parse(&ctx, "ℕ ~ <PosInt Radix LittleEndian> ~ <Seq <Digit DstRadix>~ℤ_2^64~machine.UInt64>")
     };
-    ctx.add_morphism(pattern,
-        Arc::new(
-            |mut node, dst_type| {
-                // todo: check src_type parameter to be ( Digit radix )
 
-                match dst_type {
-                    TypeTerm::App(args) => {
-                        if args.len() > 1 {
-                            match args[1] {
-                                TypeTerm::Num(_radix) => {
-                                    /* FIXME
-                                    PTYListController::for_node(
-                                        &mut node,
-                                        Some(','),
-                                        None,
-                                    );
+    ctx.write().unwrap().morphisms.add_morphism(
+        morphism_type,
+        {
+            let ctx = ctx.clone();
+            move |src_rt, σ| {
+                let src_digits = ReprTree::descend(
+                    &src_rt,
+                    Context::parse(&ctx, "
+                            <PosInt Radix BigEndian>
+                            ~<Seq <Digit Radix>~ℤ_2^64~machine.UInt64 >
+                        ")
+                    .apply_substitution(&|k|σ.get(k).cloned()).clone()
+                ).expect("cant descend")
+                    .read().unwrap()
+                    .view_seq::< usize >();
 
-                                    PTYListStyle::for_node(
-                                        &mut node,
-                                        ("0d", "", "")
-                                    );
-*/
-                                    Some(node)
-                                },
-                                _ => None
-                            }
-                        } else {
-                            None
-                        }
-                    }
-                    _ => None
-                }
+                src_rt.write().unwrap().insert_leaf(
+                        vec![
+                            Context::parse(&ctx, "<PosInt Radix LittleEndian>")
+                                .apply_substitution(&|k|σ.get(k).cloned()).clone(),
+                            Context::parse(&ctx, "<Seq <Digit Radix>>")
+                                .apply_substitution(&|k|σ.get(k).cloned()).clone(),
+                            Context::parse(&ctx, "<Seq ℤ_2^64>"),
+                            Context::parse(&ctx, "<Seq machine.UInt64>")
+                        ].into_iter(),
+
+                        ReprLeaf::from_view( src_digits.reverse() )
+                    );
             }
-        )
+        }
     );
 
-    ctx.add_node_ctor(
-        "PosInt", Arc::new(
-            |ctx0: Arc<RwLock<Context>>, dst_typ: TypeTerm, depth: OuterViewPort<dyn SingletonView<Item = usize>>| {
-                match dst_typ.clone() {
-                    TypeTerm::App(args) => {
-                        if args.len() > 1 {
-                            match args[1] {
-                                TypeTerm::Num(radix) => {
-                                    let ctx = ctx0.read().unwrap();
-                                    let mut node = Context::make_node(
-                                        &ctx0,
-                                        TypeTerm::App(vec![
-                                            TypeTerm::TypeID(ctx.get_typeid("List").unwrap()),
-                                            TypeTerm::TypeID(
-                                                ctx.get_typeid("Digit").unwrap()
-                                            )
-                                                .num_arg(radix)
-                                                .clone()
-                                                .into()
-                                        ]),
-                                        depth.map(|d| d+1)
-                                    ).unwrap();
 
-                                    node = node.morph(dst_typ);
 
-                                    Some(node)
-                                }
-                                _ => None
-                            }
-                        } else {
-                            None
-                        }
-                    }
-                    _ => None
-                }
+
+    let morphism_type = MorphismType {
+        src_type: Context::parse(&ctx, "ℕ ~ <PosInt Radix LittleEndian> ~ <Seq <Digit SrcRadix>~ℤ_2^64~machine.UInt64>"),
+        dst_type: Context::parse(&ctx, "ℕ ~ <PosInt Radix BigEndian> ~ <Seq <Digit DstRadix>~ℤ_2^64~machine.UInt64>")
+    };
+
+    ctx.write().unwrap().morphisms.add_morphism(
+        morphism_type,
+        {
+            let ctx = ctx.clone();
+            move |src_rt, σ| {
+                let src_digits = ReprTree::descend(
+                    &src_rt,
+                    Context::parse(&ctx, "
+                            <PosInt Radix LittleEndian>
+                            ~<Seq <Digit Radix>~ℤ_2^64~machine.UInt64 >
+                        ")
+                    .apply_substitution(&|k|σ.get(k).cloned()).clone()
+                ).expect("cant descend")
+                    .read().unwrap()
+                    .view_seq::< usize >();
+
+                src_rt.write().unwrap().insert_leaf(
+                        vec![
+                            Context::parse(&ctx, "<PosInt Radix BigEndian>")
+                                .apply_substitution(&|k|σ.get(k).cloned()).clone(),
+                            Context::parse(&ctx, "<Seq <Digit Radix>>")
+                                .apply_substitution(&|k|σ.get(k).cloned()).clone(),
+                            Context::parse(&ctx, "<Seq ℤ_2^64>"),
+                            Context::parse(&ctx, "<Seq machine.UInt64>")
+                        ].into_iter(),
+
+                        ReprLeaf::from_view( src_digits.reverse() )
+                    );
             }
-        )
+        }
+    );
+
+
+
+
+    let morphism_type = MorphismType {
+        src_type: Context::parse(&ctx, "ℕ ~ <PosInt SrcRadix LittleEndian> ~ <Seq <Digit SrcRadix>~ℤ_2^64~machine.UInt64>"),
+        dst_type: Context::parse(&ctx, "ℕ ~ <PosInt DstRadix LittleEndian> ~ <Seq <Digit DstRadix>~ℤ_2^64~machine.UInt64>")
+    };
+
+    ctx.write().unwrap().morphisms.add_morphism(
+        morphism_type,
+        {
+            let ctx = ctx.clone();
+            move |src_rt, σ| {
+                let src_radix = match σ.get(&laddertypes::TypeID::Var(
+                    ctx.read().unwrap().get_var_typeid("SrcRadix").unwrap()
+                )) {
+                    Some(laddertypes::TypeTerm::Num(n)) => *n as usize,
+                    _ => 0
+                };
+
+                let dst_radix = match σ.get(&laddertypes::TypeID::Var(
+                    ctx.read().unwrap().get_var_typeid("DstRadix").unwrap()
+                )) {
+                    Some(laddertypes::TypeTerm::Num(n)) => *n as usize,
+                    _ => 0
+                };
+
+                let src_digits_rt = ReprTree::descend(
+                    src_rt,
+                    Context::parse(&ctx, "
+                           <PosInt SrcRadix LittleEndian>
+                         ~ <Seq <Digit SrcRadix> ~ ℤ_2^64 ~ machine.UInt64 >"
+                    ).apply_substitution(&|k|σ.get(k).cloned()).clone()
+                ).expect("cant descend repr tree");
+
+                let dst_digits_port =
+                    src_digits_rt.read().unwrap()
+                        .view_seq::<usize>()
+                        .to_positional_uint( src_radix )
+                        .transform_radix( dst_radix )
+                ;
+
+                src_rt.write().unwrap()
+                    .insert_leaf(
+                        vec![
+                            Context::parse(&ctx, "<PosInt DstRadix LittleEndian>").apply_substitution(&|k|σ.get(k).cloned()).clone(),
+                            Context::parse(&ctx, "<Seq <Digit DstRadix>>").apply_substitution(&|k|σ.get(k).cloned()).clone(),
+                            Context::parse(&ctx, "<Seq ℤ_2^64>"),
+                            Context::parse(&ctx, "<Seq machine.UInt64>"),
+                        ].into_iter(),
+                        ReprLeaf::from_view(dst_digits_port)
+                    );
+            }
+        }
     );
-    */
-    /* 
-    ctx.add_typename("Date".into());
-    ctx.add_typename("ISO-8601".into());
-    ctx.add_typename("TimeSince".into());
-    ctx.add_typename("UnixEpoch".into());
-    ctx.add_typename("AnnoDomini".into());
-    ctx.add_typename("Epoch".into());
-    ctx.add_typename("Duration".into());
-    ctx.add_typename("Seconds".into());
-    ctx.add_typename("ℕ".into());
-    */
 }
 
diff --git a/lib-nested-core/src/editors/integer/mod.rs b/lib-nested-core/src/editors/integer/mod.rs
index 70b0759..e86a431 100644
--- a/lib-nested-core/src/editors/integer/mod.rs
+++ b/lib-nested-core/src/editors/integer/mod.rs
@@ -10,3 +10,139 @@ pub use {
     ctx::init_ctx
 };
 
+//<<<<>>>><<>><><<>><<<*>>><<>><><<>><<<<>>>>
+
+use {
+    r3vi::{
+        view::{
+            View, ViewPort, OuterViewPort,
+            Observer,
+            ObserverBroadcast,
+            sequence::*
+        }
+    },
+    crate::{
+        editors::integer::radix::{
+            PosIntProjections
+        }
+    },
+    std::sync::{Arc, RwLock}
+};
+
+pub trait PositionalUInt : SequenceView<Item = usize> {
+    fn get_radix(&self) -> usize;
+    fn get_value(&self) -> usize {
+        let mut val = 0;
+        let mut r = 1;
+        for i in 0..self.len().unwrap_or(0) {
+            val += r * self.get(&i).unwrap();
+            r *= self.get_radix();
+        }
+
+        val  
+    }
+}
+
+impl<V: PositionalUInt> PositionalUInt for RwLock<V> {
+    fn get_radix(&self) -> usize {
+        self.read().unwrap().get_radix()
+    }
+}
+
+struct PosUIntFromDigits {
+    radix: usize,
+    src_digits: Option<Arc<dyn SequenceView<Item = usize>>>,
+    cast: Arc<RwLock<ObserverBroadcast<dyn PositionalUInt>>>
+}
+
+impl View for PosUIntFromDigits {
+    type Msg = usize;
+}
+
+impl SequenceView for PosUIntFromDigits {
+    type Item = usize;
+
+    fn get(&self, idx: &usize) -> Option<usize> {
+        self.src_digits.get(idx)
+    }
+
+    fn len(&self) -> Option<usize> {
+        self.src_digits.len()
+    }
+}
+
+impl PositionalUInt for PosUIntFromDigits {
+    fn get_radix(&self) -> usize {
+        self.radix
+    }
+}
+
+impl Observer<dyn SequenceView<Item = usize>> for PosUIntFromDigits {
+    fn reset(&mut self, new_src: Option<Arc<dyn SequenceView<Item = usize>>>) {
+        self.src_digits = new_src;
+//        self.cast.write().unwrap().notify(0);
+    }
+
+    fn notify(&mut self, idx: &usize) {
+        self.cast.write().unwrap().notify(idx);
+    }
+}
+
+//<<<<>>>><<>><><<>><<<*>>><<>><><<>><<<<>>>>
+
+pub trait DigitSeqProjection {
+    fn to_positional_uint(&self, radix: usize) -> OuterViewPort<dyn PositionalUInt>;
+}
+
+impl DigitSeqProjection for OuterViewPort<dyn SequenceView<Item = usize>> {
+    fn to_positional_uint(&self, radix: usize) -> OuterViewPort<dyn PositionalUInt> {
+        let port = ViewPort::new();
+        port.add_update_hook(Arc::new(self.0.clone()));
+
+        let proj = Arc::new(RwLock::new(PosUIntFromDigits {
+            radix,
+            src_digits: None,
+            cast: port.inner().get_broadcast()
+        }));
+
+        self.add_observer(proj.clone());
+        port.set_view(Some(proj));
+        port.into_outer()
+    }
+}
+
+//<<<<>>>><<>><><<>><<<*>>><<>><><<>><<<<>>>>
+
+struct PosUIntToDigits {
+    src: Option<Arc<dyn PositionalUInt>>,
+    cast: Arc<RwLock<ObserverBroadcast<dyn SequenceView<Item = usize>>>>
+}
+
+impl View for PosUIntToDigits {
+    type Msg = usize;
+}
+
+impl SequenceView for PosUIntToDigits {
+    type Item = usize;
+
+    fn get(&self, idx: &usize) -> Option<usize> {
+        self.src.get(idx)
+    }
+
+    fn len(&self) -> Option<usize> {
+        self.src.len()
+    }
+}
+
+impl Observer<dyn PositionalUInt> for PosUIntToDigits {
+    fn reset(&mut self, view: Option<Arc<dyn PositionalUInt>>) {
+        self.src = view;
+//        self.cast.notify_all();
+    }
+
+    fn notify(&mut self, idx: &usize) {
+        self.cast.notify(idx);
+    }
+}
+
+
diff --git a/lib-nested-core/src/editors/integer/radix.rs b/lib-nested-core/src/editors/integer/radix.rs
index bcc12da..db3506c 100644
--- a/lib-nested-core/src/editors/integer/radix.rs
+++ b/lib-nested-core/src/editors/integer/radix.rs
@@ -1,69 +1,127 @@
 use {
     r3vi::{
         view::{
+            View, ViewPort,
             InnerViewPort, Observer, OuterViewPort,
+            ObserverBroadcast,
             sequence::*,
+            list::*
         },
         buffer::{vec::*}
     },
+    crate::{
+        editors::integer::{
+            PositionalUInt
+        },
+        repr_tree::{ReprTree, ReprLeaf}
+    },
     std::sync::{Arc, RwLock},
 };
 
+//<<<<>>>><<>><><<>><<<*>>><<>><><<>><<<<>>>>
+
+pub trait PosIntProjections {
+    fn transform_radix(&self, dst_radix: usize) -> OuterViewPort<dyn SequenceView<Item = usize>>;
+//    fn to_digits(&self) -> OuterViewPort<dyn SequenceView<Item = usize>>;
+}
+
+impl PosIntProjections for OuterViewPort<dyn PositionalUInt> {
+    fn transform_radix(&self, dst_radix: usize) -> OuterViewPort<dyn SequenceView<Item = usize>> {
+        let port = ViewPort::<dyn SequenceView<Item = usize>>::new();
+        port.add_update_hook(Arc::new(self.0.clone()));
+
+//        let mut vec_port = ViewPort::new();
+        let proj = Arc::new(RwLock::new(RadixProjection {
+            src: None,
+            dst_radix,
+            dst_digits: VecBuffer::new(),
+            cast: port.inner().get_broadcast()
+        }));
+
+        self.add_observer(proj.clone());
+        port.set_view(Some(proj as Arc<dyn SequenceView<Item = usize>>));
+        port.into_outer()
+    }
+/*
+    fn to_digits(&self) -> OuterViewPort<dyn SequenceView<Item = usize>> {
+        let port = ViewPort::new();
+        port.add_update_hook(Arc::new(self.0.clone()));
+        let proj = Arc::new(RwLock::new(PosUIntToDigits {
+            src: None,
+            cast: port.inner().get_broadcast()
+        }));
+        self.add_observer(proj.clone());
+        port.inner().set_view(Some(proj));
+        port.into_outer()
+    }
+    */
+}
+
+//<<<<>>>><<>><><<>><<<*>>><<>><><<>><<<<>>>>
+
 pub struct RadixProjection {
-    src_radix: usize,
+    src: Option<Arc<dyn PositionalUInt>>,
     dst_radix: usize,
-    src_digits: Option<Arc<dyn SequenceView<Item = usize>>>,
-    dst_digits: RwLock<VecBuffer<usize>>,
+    dst_digits: VecBuffer<usize>,
+    cast: Arc<RwLock<ObserverBroadcast<dyn SequenceView<Item = usize>>>>
+}
+
+impl View for RadixProjection {
+    type Msg = usize;
+}
+
+impl SequenceView for RadixProjection {
+    type Item = usize;
+
+    fn get(&self, idx: &usize) -> Option<usize> {
+        if *idx < self.dst_digits.len() {
+            Some(self.dst_digits.get(*idx))
+        } else {
+            None
+        }
+    }
+
+    fn len(&self) -> Option<usize> {
+        Some(self.dst_digits.len())
+    }
+}
+
+impl PositionalUInt for RadixProjection {
+    fn get_radix(&self) -> usize {
+        self.dst_radix
+    }
+}
+
+impl Observer< dyn PositionalUInt > for RadixProjection {
+    fn reset(&mut self, view: Option<Arc<dyn PositionalUInt>>) {
+        self.src = view;
+        self.update();
+    }
+
+    fn notify(&mut self, idx: &usize) {
+        self.update();
+        // self.update_digit(idx)
+    }
 }
 
 impl RadixProjection {
-    pub fn new(
-        // static parameters
-        //---
-        src_radix: usize,
-        dst_radix: usize,
-        //---
+    /// recalculate everything
+    fn update(&mut self) {
+//       let mut dst = self.dst_digits;
+        let old_len = self.dst_digits.len();
+        self.dst_digits.clear();
 
-        // dynamic parameters
-        //---
-        // input
-        src_digits: OuterViewPort<dyn SequenceView<Item = usize>>,
-        // output
-        dst_digits: InnerViewPort<RwLock<Vec<usize>>>,
-        //---
-    ) -> Arc<RwLock<Self>> {
-        dst_digits.0.add_update_hook(Arc::new(src_digits.0.clone()));
-        let proj = Arc::new(RwLock::new(RadixProjection {
-            src_radix,
-            dst_radix,
-            src_digits: None,
-            dst_digits: RwLock::new(VecBuffer::with_port(dst_digits)),
-        }));
-        src_digits.add_observer(proj.clone());
-        proj
-    }
-
-    fn machine_int(&self) -> usize {
-        let mut val = 0;
-        let mut r = 1;
-        for i in 0..self.src_digits.len().unwrap_or(0) {
-            val += r * self.src_digits.get(&i).unwrap();
-            r *= self.src_radix;
+        if let Some(src) = self.src.as_ref() {
+            let mut val = src.get_value();
+            while val > 0 {
+                self.dst_digits.push(val % self.dst_radix);
+                val /= self.dst_radix;
+            }
         }
 
-        val
-    }
-
-    // recalculate everything
-    fn update(&self) {
-        let mut dst = self.dst_digits.write().unwrap();
-        dst.clear();
-
-        let mut val = self.machine_int();
-
-        while val > 0 {
-            dst.push(val % self.dst_radix);
-            val /= self.dst_radix;
+        let new_len = self.dst_digits.len();
+        for i in 0 .. usize::max(old_len, new_len) {
+             self.cast.write().unwrap().notify(&i);
         }
     }
 
@@ -84,18 +142,3 @@ impl RadixProjection {
     }
 }
 
-impl Observer<dyn SequenceView<Item = usize>> for RadixProjection {
-    fn reset(&mut self, view: Option<Arc<dyn SequenceView<Item = usize>>>) {
-        self.src_digits = view;
-    }
-
-    fn notify(&mut self, _idx: &usize) {
-        // todo:
-        // src digit i changed.
-        // which dst-digits does it affect?
-        // update dst-digit j:
-
-        // ...but for now the easy way
-        self.update();
-    }
-}
diff --git a/lib-nested-core/src/editors/list/ctx.rs b/lib-nested-core/src/editors/list/ctx.rs
index 79943db..808e28c 100644
--- a/lib-nested-core/src/editors/list/ctx.rs
+++ b/lib-nested-core/src/editors/list/ctx.rs
@@ -92,6 +92,41 @@ pub fn init_ctx(ctx: Arc<RwLock<Context>>) {
         }
     );
 
+    let mt = crate::repr_tree::MorphismType {
+        src_type: Context::parse(&ctx, "<List <Digit 16>>~EditTree"),
+        dst_type: Context::parse(&ctx, "<List <Digit 16>~Char>")
+    };
+    ctx.write().unwrap().morphisms.add_morphism(
+        mt,
+        {
+            let ctx = ctx.clone();
+            move |src_rt, σ| {
+                let edittree =
+                    src_rt
+                        .descend(Context::parse(&ctx, "EditTree")).unwrap()
+                        .singleton_buffer::<EditTree>();
+
+                let list_edit = edittree.get().get_edit::< ListEditor >().unwrap();
+                let edittree_items = list_edit.read().unwrap().data.get_port().to_list();
+                src_rt.write().unwrap().insert_leaf(
+                    vec![ Context::parse(&ctx, "<List Char>") ].into_iter(),
+                    ReprLeaf::from_view(
+                        edittree_items
+                            .map(
+                                |edittree_char|
+                                    edittree_char
+                                    .read().unwrap()
+                                    .get_edit::<crate::editors::digit::editor::DigitEditor>().unwrap()
+                                    .read().unwrap()
+                                    .get_char()
+                            )
+                    )
+                );
+            }
+        }
+    );
+
+
 
     let mt = crate::repr_tree::MorphismType {
         src_type: Context::parse(&ctx, "<List Char>"),
diff --git a/lib-nested-core/src/lib.rs b/lib-nested-core/src/lib.rs
index bca12dc..b942062 100644
--- a/lib-nested-core/src/lib.rs
+++ b/lib-nested-core/src/lib.rs
@@ -1,4 +1,6 @@
 
+#![feature(trait_upcasting)]
+
 pub mod repr_tree;
 pub mod edit_tree;
 pub mod editors;
diff --git a/lib-nested-core/src/repr_tree/mod.rs b/lib-nested-core/src/repr_tree/mod.rs
index 3b58eb8..a5c47a8 100644
--- a/lib-nested-core/src/repr_tree/mod.rs
+++ b/lib-nested-core/src/repr_tree/mod.rs
@@ -396,6 +396,10 @@ impl ReprTree {
     pub fn view_u64(&self) -> OuterViewPort<dyn SingletonView<Item = u64>> {
         self.get_port::<dyn SingletonView<Item = u64>>().expect("no u64-view available")
     }
+
+    pub fn view_usize(&self) -> OuterViewPort<dyn SingletonView<Item = usize>> {
+        self.get_port::<dyn SingletonView<Item = usize>>().expect("no usize-view available")
+    }
 }
 
 
@@ -412,6 +416,7 @@ pub trait ReprTreeExt {
     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 view_usize(&self) -> OuterViewPort<dyn SingletonView<Item = usize>>;
 
     fn singleton_buffer<T: Clone + Send + Sync + 'static>(&self) -> SingletonBuffer<T>;
     fn vec_buffer<T: Clone + Send + Sync + 'static>(&self) -> VecBuffer<T>;
@@ -446,6 +451,10 @@ impl ReprTreeExt for Arc<RwLock<ReprTree>> {
         self.read().unwrap().view_u64()
     }
 
+    fn view_usize(&self) -> OuterViewPort<dyn SingletonView<Item = usize>> {
+        self.read().unwrap().view_usize()
+    }
+
     fn singleton_buffer<T: Clone + Send + Sync + 'static>(&self) -> SingletonBuffer<T> {
         self.write().unwrap().singleton_buffer::<T>().expect("")
     }