diff --git a/Cargo.toml b/Cargo.toml
index c3f2dbd..fe2b93b 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -12,4 +12,5 @@ members = [
     "examples/tty-04-posint",
     "examples/tty-05-dictionary",
     "examples/tty-06-lines",
+    "examples/tty-07-color",
 ]
diff --git a/examples/tty-04-posint/src/main.rs b/examples/tty-04-posint/src/main.rs
index 5f9e032..1a125b9 100644
--- a/examples/tty-04-posint/src/main.rs
+++ b/examples/tty-04-posint/src/main.rs
@@ -39,8 +39,8 @@ async fn main() {
      */
     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::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);
 
@@ -49,23 +49,28 @@ async fn main() {
      */
     let int_builder = ReprTreeBuilder::new( ctx.clone() )
             .require(Context::parse(&ctx,
-                "ℕ ~ <PosInt 16 BigEndian> ~ EditTree"))
+                //"ℕ ~ <PosInt 16 BigEndian> ~ <Seq <Digit 16>> ~ <List <Digit 16>> ~
+                "<List  <Digit 16>> ~ <List Char> ~ EditTree"))
+            /*
             .require(Context::parse(&ctx,
                 "ℕ ~ <PosInt 10 BigEndian> ~ EditTree"))
             .require(Context::parse(&ctx,
                 "ℕ ~ <PosInt 8 BigEndian> ~ EditTree"))
             .require(Context::parse(&ctx,
                 "ℕ ~ <PosInt 2 BigEndian> ~ EditTree"))
+                */
                 ;
 
     let mut rt_int = nested::repr_tree::ReprTree::from_str("3");
     rt_int.write().unwrap().set_halo(
         /* HALO TYPE (append to top of type ladder) */
-        Context::parse(&ctx, "
+        Context::parse(&ctx, /*"
               ℕ
             ~ <PosInt 16 BigEndian>
             ~ <Seq <Digit 16>>
             ~ <List <Digit 16>>
+            */
+            " <List <Digit 16>>
             ~ <List Char>
         ")
     );
@@ -102,7 +107,7 @@ async fn main() {
     let first_idx : usize = 0;
     int_builder.update( &rt_int, int_builder.required_leaves[first_idx].clone() );
 
-    edittree.goto(TreeCursor{
+    edittree.goto(TreeCursor {
         leaf_mode: nested::editors::list::ListCursorMode::Insert,
         tree_addr: vec![first_idx as isize, 0]
     });
@@ -155,7 +160,6 @@ async fn main() {
             let halo_type = rt_edittree.read().unwrap().get_halo_type().clone();
             let edittree = rt_edittree.edittree( &ctx );
 
-
             let box_port = ViewPort::new();
             let ascii_box = nested_tty::widgets::ascii_box::AsciiBox::new(
                 Vector2::new(30, 1),
diff --git a/examples/tty-06-lines/src/lines.rs b/examples/tty-06-lines/src/lines.rs
index a57adfd..7419c4e 100644
--- a/examples/tty-06-lines/src/lines.rs
+++ b/examples/tty-06-lines/src/lines.rs
@@ -85,6 +85,7 @@ impl LinesEditor {
                 }
             },
         );
+
         ctx.write()
             .unwrap()
             .morphisms
@@ -120,7 +121,9 @@ impl LinesEditor {
             .flatten();
 
         let mut list_edit = list_edit.into_node(depth_port);
-        nested_tty::editors::list::PTYListController::for_node(&mut list_edit, Some('\n'), None);
+        {
+            nested_tty::editors::list::PTYListController::for_node(&mut list_edit, Some('\n'), None);
+        }
         list_edit
             .disp
             .view
diff --git a/examples/tty-07-color/Cargo.toml b/examples/tty-07-color/Cargo.toml
index 53db651..d5299b8 100644
--- a/examples/tty-07-color/Cargo.toml
+++ b/examples/tty-07-color/Cargo.toml
@@ -1,5 +1,5 @@
 [package]
-name = "tty-06-color"
+name = "tty-07-color"
 version = "0.1.0"
 edition = "2021"
 
@@ -16,4 +16,3 @@ cgmath = "*"
 [dependencies.async-std]
 version = "1.9.0"
 features = ["unstable", "attributes"]
-
diff --git a/examples/tty-07-color/src/main.rs b/examples/tty-07-color/src/main.rs
index e02ae87..afe5403 100644
--- a/examples/tty-07-color/src/main.rs
+++ b/examples/tty-07-color/src/main.rs
@@ -10,7 +10,7 @@ use {
         editors::{
             ObjCommander
         },
-        repr_tree::{Context, ReprTree, ReprTreeExt, ReprLeaf},
+        repr_tree::{Context, ReprTree, ReprTreeBuilder, ReprTreeExt, ReprTreeArc, ReprLeaf},
         edit_tree::{EditTree, TreeNav, TreeCursor}
     },
     nested_tty::{
@@ -46,139 +46,57 @@ async fn main() {
         Context::parse(&ctx, "<Vec EditTree>")
     );
 
-    let mut red = nested::repr_tree::ReprTree::from_str(Context::parse(&ctx, "
-            ℕ ~ <PosInt 10 BigEndian> ~ <Seq <Digit 10>> ~ <List <Digit 10> ~ Char> ~ <Vec Char>
-        "),
-        "221"
-    );
-    ctx.read().unwrap().apply_morphism( &red,
-        &laddertypes::MorphismType {
-            src_type: Context::parse(&ctx, "ℕ ~ <PosInt 10 BigEndian> ~ <Seq~List <Digit 10> ~ Char > ~ <Vec Char>"),
-            dst_type: Context::parse(&ctx, "ℕ ~ <PosInt 16 BigEndian> ~ <Seq~List <Digit 16> ~ Char > ~ EditTree")
-        });
-    let red_edit = ctx.read().unwrap().setup_edittree(
-        red.descend(Context::parse(&ctx, "
-                ℕ ~ <PosInt 16 BigEndian> ~ <Seq~List <Digit 16>~Char>
-            ")).unwrap(),
-        SingletonBuffer::new(0).get_port()
-    ).unwrap();
+    let channel_builder = ReprTreeBuilder::new(ctx.clone())
+        .require(Context::parse(&ctx, "
+            ℕ ~ <PosInt 10 BigEndian> ~ EditTree
+        "))
+        .require(Context::parse(&ctx, "
+            ℕ ~ <PosInt 16 BigEndian> ~ EditTree
+        "));
 
-    let mut green = nested::repr_tree::ReprTree::from_str(Context::parse(&ctx, "
-            ℕ ~ <PosInt 10 BigEndian> ~ <Seq <Digit 10>> ~ <List <Digit 10> ~ Char> ~ <Vec Char>
-        "),
-        "220"
-    );
-    ctx.read().unwrap().apply_morphism( &green,
-        &laddertypes::MorphismType {
-            src_type: Context::parse(&ctx, "ℕ ~ <PosInt 10 BigEndian> ~ <Seq~List <Digit 10> ~ Char > ~ <Vec Char>"),
-            dst_type: Context::parse(&ctx, "ℕ ~ <PosInt 16 BigEndian> ~ <Seq~List <Digit 16> ~ Char > ~ EditTree")
-        });
-     let green_edit = ctx.read().unwrap().setup_edittree(green.descend(Context::parse(&ctx, "
-                ℕ ~ <PosInt 16 BigEndian> ~ <Seq~List <Digit 16>~Char>
-            ")).unwrap(),
-        SingletonBuffer::new(0).get_port()
-    ).unwrap();
+    let mut red = nested::repr_tree::ReprTree::from_str("221");
+    red.write().unwrap().set_halo(Context::parse(&ctx, "
+        ℕ ~ <PosInt 10 BigEndian> ~ <Seq~List <Digit 10>~Char>
+    "));
+    red = channel_builder.build_from(red).expect("");
 
-    
-    let mut blue = nested::repr_tree::ReprTree::from_str(Context::parse(&ctx, "
-            ℕ ~ <PosInt 10 BigEndian> ~ <Seq <Digit 10>> ~ <List <Digit 10> ~ Char> ~ <Vec Char>
-        "),
-        "5"
-    );
-    ctx.read().unwrap().apply_morphism( &blue,
-        &laddertypes::MorphismType {
-            src_type: Context::parse(&ctx, "ℕ ~ <PosInt 10 BigEndian> ~ <Seq~List <Digit 10> ~ Char > ~ <Vec Char>"),
-            dst_type: Context::parse(&ctx, "ℕ ~ <PosInt 16 BigEndian> ~ <Seq~List <Digit 16> ~ Char > ~ EditTree")
-        });
-    let blue_edit = ctx.read().unwrap().setup_edittree(
-        blue.descend(Context::parse(&ctx, "
-                ℕ ~ <PosInt 16 BigEndian> ~ <Seq~List <Digit 16>~Char>
-            ")).unwrap(),
-        SingletonBuffer::new(0).get_port()
-    ).unwrap();
+    let mut green = nested::repr_tree::ReprTree::from_str("220");
+    green.write().unwrap().set_halo(Context::parse(&ctx, "
+        ℕ ~ <PosInt 10 BigEndian> ~ <Seq~List <Digit 10>~Char>
+    "));
+    green = channel_builder.build_from(green).expect("");
 
+    let mut blue = nested::repr_tree::ReprTree::from_str("150");
+    blue.write().unwrap().set_halo(Context::parse(&ctx, "
+        ℕ ~ <PosInt 10 BigEndian> ~ <Seq~List <Digit 10>~Char>
+    "));
+    blue = channel_builder.build_from(blue).expect("");
+
+    let mut color_builder = ReprTreeBuilder::new(ctx.clone())
+        .require(Context::parse(&ctx, "<List ℕ ~ <PosInt 16 BigEndian>> ~ EditTree"))
+        .require(Context::parse(&ctx, "<List ℕ ~ <PosInt 10 BigEndian>> ~ EditTree"))
+        ;
 
-    eprintln!("======\n   M A K E    L I S T    E D I T O R\n======\n");
-    
     let mut color = nested::repr_tree::ReprTree::new_arc(
         Context::parse(&ctx, "<List ℕ>")
     );
-
     color.insert_leaf(
         Context::parse(&ctx, "
-                <List   ℕ
-                      ~ <PosInt 16 BigEndian>
-                      ~ <Seq <Digit 16>>
-                      ~ <List  <Digit 16>
-                              ~ Char >
-                >
-                ~ <List EditTree>
-                ~ <Vec EditTree>
+                < List   ℕ ~ ReprTree >
+                ~ < Vec ReprTree >
             "),
-
-        ReprLeaf::from_vec_buffer(VecBuffer::<
-            Arc<RwLock< EditTree >>
-        >::with_data(vec![
-            red_edit.get(),
-            green_edit.get(),
-            blue_edit.get()
-        ]))
+        ReprLeaf::from_vec_buffer(VecBuffer::<ReprTreeArc>::with_data(
+            vec![ red, green, blue ])
+        )
+    );
+/*
+    color.attach_leaf_to(
+        Context::parse(&ctx, "< List ℕ ~ <PosInt 10 BigEndian> ~ EditTre >"),
+        color.descend(Context::parse(&ctx, "<List ℕ ~ ReprTree> ~ <Vec ReprTree>"))
+            .expect("descend")
+            .
     );
-    ctx.read().unwrap().apply_morphism(
-        &color,
-        &laddertypes::MorphismType {
-            src_type: Context::parse(&ctx, "<List ℕ ~ <PosInt 16 BigEndian> ~ <Seq~List <Digit 16> ~ Char > ~ EditTree > ~ <Vec EditTree>"),
-            dst_type: Context::parse(&ctx, "<List ℕ ~ <PosInt 16 BigEndian> ~ <Seq~List <Digit 16> ~ Char > > ~ EditTree")
-        });
-    let edit = ctx.read().unwrap().setup_edittree(
-        color.descend(Context::parse(&ctx, "
-                <List   ℕ
-                      ~ < PosInt 16 BigEndian >
-                      ~ < Seq~List   <Digit 16>
-                                   ~ Char >
-                >
-            ")).unwrap(),
-        SingletonBuffer::new(0).get_port()
-    ).unwrap();
-
-
-
-eprintln!(" edittree => list list char ");
-     ctx.read().unwrap().apply_morphism(
-        &color,
-        &laddertypes::MorphismType {
-            src_type: Context::parse(&ctx, "<List ℕ ~ <PosInt 16 BigEndian> ~ <Seq~List <Digit 16> ~ Char > > ~ EditTree"),
-            dst_type: Context::parse(&ctx, "<List ℕ ~ <PosInt 16 BigEndian> ~ <Seq~List <Digit 16> ~ Char > >")
-        });
-
-eprintln!("list char ==> list u64");
-    ctx.read().unwrap().apply_morphism(
-        &color,
-        &laddertypes::MorphismType {
-            src_type: Context::parse(&ctx, "<List ℕ ~ <PosInt 16 BigEndian> ~ <Seq~List <Digit 16> ~ Char>>"),
-            dst_type: Context::parse(&ctx, "<List ℕ ~ <PosInt 16 BigEndian> ~ <Seq~List <Digit 16> ~ ℤ_2^64 ~ machine.UInt64>>")
-        });
-return;
-
-    ctx.read().unwrap().apply_morphism(
-        &color,
-        &laddertypes::MorphismType {
-            src_type: Context::parse(&ctx, "<List ℕ ~ <PosInt 16 BigEndian> ~ <Seq~List <Digit 16> ~ ℤ_2^64 ~ machine.UInt64 > >"),
-            dst_type: Context::parse(&ctx, "<List ℕ ~ <PosInt 10 BigEndian> ~ <Seq~List <Digit 10> ~ Char > >")
-        });
-    /*
-    let edit2 = ctx.read().unwrap().setup_edittree(
-        color.descend(Context::parse(&ctx, "
-                <List   ℕ
-                      ~ < PosInt 10 BigEndian >
-                      ~ < Seq~List   <Digit 10>
-                                   ~ Char >
-                >
-            ")).unwrap(),
-        SingletonBuffer::new(0).get_port()
-    ).unwrap();
 */
-
     return;
 
     /* setup terminal
@@ -187,12 +105,12 @@ return;
         /* event handler
          */
         let ctx = ctx.clone();
-        let edit = edit.get().clone();
+        //let edit = edit.get().clone();
+
+       // edit.write().unwrap().goto(TreeCursor::home());
 
-        edit.write().unwrap().goto(TreeCursor::home());
-        
         move |ev| {
-            edit.write().unwrap().send_cmd_obj( ev.to_repr_tree(&ctx) );
+      //      edit.write().unwrap().send_cmd_obj( ev.to_repr_tree(&ctx) );
         }
     });
 
@@ -213,7 +131,7 @@ return;
             let halo_type = rt_edittree.read().unwrap().get_halo_type().clone();
             let edittree = rt_edittree.read().unwrap().get_view::<dyn r3vi::view::singleton::SingletonView<Item = Arc<RwLock<EditTree>>>>().unwrap().get().read().unwrap().clone();
 
-            comp.push(  nested_tty::make_label( &ctx.read().unwrap().type_term_to_str(&halo_type) ) 
+            comp.push(  nested_tty::make_label( &ctx.read().unwrap().type_term_to_str(&halo_type) )
                 .map_item(|_pt, atom| atom.add_style_front(TerminalStyle::fg_color((90,90,90))))
                 .offset(Vector2::new(1,y)));
 
@@ -221,12 +139,11 @@ return;
                 .offset(Vector2::new(1,y+1)));
         }
 
-        show_edit_tree( &ctx, &mut comp, &color.descend(Context::parse(&ctx, "<List ℕ ~ <PosInt 16 BigEndian> ~ <Seq~List <Digit 16>~Char>>")).unwrap(), 1 );        
-        show_edit_tree( &ctx, &mut comp, &color.descend(Context::parse(&ctx, "<List ℕ ~ <PosInt 10 BigEndian> ~ <Seq~List <Digit 10>~Char>>")).unwrap(), 3 );
+    //    show_edit_tree( &ctx, &mut comp, &color.descend(Context::parse(&ctx, "<List ℕ ~ <PosInt 16 BigEndian> ~ <Seq~List <Digit 16>~Char>>")).unwrap(), 1 );
+    //    show_edit_tree( &ctx, &mut comp, &color.descend(Context::parse(&ctx, "<List ℕ ~ <PosInt 10 BigEndian> ~ <Seq~List <Digit 10>~Char>>")).unwrap(), 3 );
     }
 
     /* 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/list/ctx.rs b/lib-nested-core/src/editors/list/ctx.rs
index 1d00b34..58ee1d5 100644
--- a/lib-nested-core/src/editors/list/ctx.rs
+++ b/lib-nested-core/src/editors/list/ctx.rs
@@ -261,7 +261,7 @@ pub fn init_ctx(ctx: Arc<RwLock<Context>>) {
     ctx.write().unwrap().add_varname("Item");
 
     let list_morph_editsetup1 = GenericReprTreeMorphism::new(
-        Context::parse(&ctx, "<List Item>~<List ReprTree>~<Vec ReprTree>"),
+        Context::parse(&ctx, "<List~Vec Item~ReprTree>"),
         Context::parse(&ctx, "<List Item>~EditTree"),
         {
             let ctx = ctx.clone();
diff --git a/lib-nested-core/src/repr_tree/builder.rs b/lib-nested-core/src/repr_tree/builder.rs
index 47002f6..ea8c541 100644
--- a/lib-nested-core/src/repr_tree/builder.rs
+++ b/lib-nested-core/src/repr_tree/builder.rs
@@ -1,23 +1,11 @@
 use {
-    r3vi::{
-        view::{
-            ViewPort, OuterViewPort,
-            AnyViewPort, AnyInnerViewPort, AnyOuterViewPort,
-            port::UpdateTask,
-            View, Observer,
-            singleton::*,
-            sequence::*,
-            list::*
-        },
-        buffer::{singleton::*, vec::*}
-    },
-    laddertypes::{TypeTerm, TypeID, sugar::*},
-    std::{
-        collections::HashMap,
-        sync::{Arc, RwLock},
-        any::Any
-    },
-    super::{Context, ReprLeaf, ReprTree, ReprTreeExt, context::{TYPEID_list, TYPEID_vec, TYPEID_char, TYPEID_u64, TYPEID_edittree}}
+    super::{context::{TYPEID_char, TYPEID_edittree, TYPEID_list, TYPEID_u64, TYPEID_vec}, Context, ReprLeaf, ReprTree, ReprTreeExt}, laddertypes::{steiner_tree, sugar::*, unparser::UnparseLadderType as _, TypeID, TypeTerm}, r3vi::{
+        buffer::{singleton::*, vec::*}, view::{
+            list::*, port::UpdateTask, sequence::*, singleton::*, AnyInnerViewPort, AnyOuterViewPort, AnyViewPort, Observer, OuterViewPort, View, ViewPort
+        }
+    }, std::{
+        any::Any, collections::HashMap, sync::{Arc, RwLock}
+    }
 };
 
 //<<<<>>>><<>><><<>><<<*>>><<>><><<>><<<<>>>>
@@ -65,8 +53,8 @@ impl ReprTreeBuilder {
 
         let morphism_base = &self.ctx.read().unwrap().morphisms;
 
-        let mt = master_leaf_type.into();
-        //eprintln!("REBUILD repr tree from {}", self.ctx.read().unwrap().type_term_to_str(&mt));
+        let mt = master_leaf_type.into().normalize().param_normalize();
+        eprintln!("REBUILD repr tree from {}", self.ctx.read().unwrap().type_term_to_str(&mt));
         let mut leaves = self.required_leaves.clone();
         leaves.retain(|t| t != &mt);
 
@@ -77,18 +65,32 @@ impl ReprTreeBuilder {
 
         if let Some( steiner_tree ) = st_problem.solve( &morphism_base ) {
             eprintln!("--> from {}", self.ctx.read().unwrap().type_term_to_str(&mt));
-            for morphism_type in steiner_tree.into_edges() {
+
+            let edges = steiner_tree.into_edges();
+            eprintln!("steiner tree has {} edges", edges.len());
+            for morphism_type in edges {
                 eprintln!("--> morph to {}",
                     self.ctx.read().unwrap().type_term_to_str(&morphism_type.dst_type));
 
-                if let Some(( morphism, mut τ, σ )) =
-                    morphism_base.find_morphism_with_subtyping( &morphism_type )
+                let mut dict = self.ctx.read().unwrap().type_dict.clone();
+
+                if let Some(morph_inst) =
+                    morphism_base.find_morphism( &morphism_type, &mut dict )
                 {
-                    let mut rt = rt.descend_create( τ ).expect("descend src repr");
-                    (morphism.setup_projection)( &mut rt, &σ );
+                    eprintln!("setup morph");
+
+                    let halo = laddertypes::common_halo(
+                        &morphism_type.src_type,
+                        &morphism_type.dst_type
+                    ).unwrap_or(TypeTerm::unit());
+                    eprintln!("halo = {}", dict.read().unwrap().unparse(&halo));
+
+                    let mut rt = rt.descend_create( halo ).expect("descend src repr");
+                    eprintln!("{}", rt.read().unwrap().fmt(&self.ctx, 0));
+                    (morph_inst.m.setup_projection)( &mut rt, &morph_inst.σ );
                 } else {
                     eprintln!("failed to get morphism");
-                    //return Err(ReprTreeError::MissingMorphism);
+                    return Err(ReprTreeError::MissingMorphism);
                 }
             }
 
diff --git a/lib-nested-core/src/repr_tree/context.rs b/lib-nested-core/src/repr_tree/context.rs
index 8254090..8fdea0a 100644
--- a/lib-nested-core/src/repr_tree/context.rs
+++ b/lib-nested-core/src/repr_tree/context.rs
@@ -53,22 +53,28 @@ pub struct Context {
 
 impl Context {
     pub fn with_parent(parent: Option<Arc<RwLock<Context>>>) -> Self {
-        Context {
-            type_dict: match parent.as_ref() {
-                Some(p) => p.read().unwrap().type_dict.clone(),
-                None => {
-                    let mut dict = BimapTypeDict::new();
-                    assert_eq!(TYPEID_reprtree, dict.add_typename("ReprTree".into()));
-                    assert_eq!(TYPEID_edittree, dict.add_typename("EditTree".into()));
-                    assert_eq!(TYPEID_char, dict.add_typename("Char".into()));
-                    assert_eq!(TYPEID_u64, dict.add_typename("machine.UInt64".into()));
-                    assert_eq!(TYPEID_list, dict.add_typename("List".into()));
-                    assert_eq!(TYPEID_vec, dict.add_typename("Vec".into()));
 
-                    Arc::new(RwLock::new(dict))
-                }
-            },
-            morphisms: MorphismBase::new(TYPEID_list),
+        let mut dict = match parent.as_ref() {
+            Some(p) => p.read().unwrap().type_dict.clone(),
+            None => {
+                let mut dict = BimapTypeDict::new();
+                assert_eq!(TYPEID_reprtree, dict.add_typename("ReprTree".into()));
+                assert_eq!(TYPEID_edittree, dict.add_typename("EditTree".into()));
+                assert_eq!(TYPEID_char, dict.add_typename("Char".into()));
+                assert_eq!(TYPEID_u64, dict.add_typename("machine.UInt64".into()));
+                assert_eq!(TYPEID_list, dict.add_typename("List".into()));
+                assert_eq!(TYPEID_vec, dict.add_typename("Vec".into()));
+
+                Arc::new(RwLock::new(dict))
+            }
+        };
+
+        Context {
+            type_dict: dict.clone(),
+            morphisms: MorphismBase::new(vec![
+                dict.parse("List").expect(""),
+                //dict.parse("Vec").expect("")
+            ]),
             nodes: HashMap::new(),
             list_types: match parent.as_ref() {
                 Some(p) => p.read().unwrap().list_types.clone(),
@@ -104,22 +110,9 @@ impl Context {
 
     pub fn apply_morphism(&self, rt: &Arc<RwLock<ReprTree>>, ty: &MorphismType) {
         if let Some(path) = self.morphisms.find_morphism_path(ty.clone().normalize()) {
-            let mut path = path.into_iter();
-            if let Some(mut src_type) = path.next() {
-                for dst_type in path {
-                    if let Some((m, mut τ, σ)) =
-                        self.morphisms
-                            .find_morphism_with_subtyping(&laddertypes::MorphismType {
-                                src_type: src_type.clone(),
-                                dst_type: dst_type.clone(),
-                            })
-                    {
-                        let mut rt = rt.descend(τ).expect("descend src repr");
-                        (m.setup_projection)(&mut rt, &σ);
-                    }
-
-                    src_type = dst_type;
-                }
+            for morph_inst in path {
+                let mut rt = rt.descend(morph_inst.halo).expect("descend src repr");
+                (morph_inst.m.setup_projection)(&mut rt, &morph_inst.σ);
             }
         } else {
             eprintln!("no path found");
diff --git a/lib-nested-core/src/repr_tree/morphism.rs b/lib-nested-core/src/repr_tree/morphism.rs
index c5e5e8a..d841d94 100644
--- a/lib-nested-core/src/repr_tree/morphism.rs
+++ b/lib-nested-core/src/repr_tree/morphism.rs
@@ -27,13 +27,19 @@ pub struct GenericReprTreeMorphism {
     >
 }
 
+impl PartialEq  for GenericReprTreeMorphism {
+    fn eq(&self, other: &Self) -> bool {
+        self.morph_type == other.morph_type
+    }
+}
+
 impl Morphism for GenericReprTreeMorphism {
     fn get_type(&self) -> MorphismType {
         self.morph_type.clone()
     }
 
-    fn list_map_morphism(&self, list_typeid: TypeID) -> Option< GenericReprTreeMorphism > {
-        self.into_list_map_dyn(list_typeid)
+    fn map_morphism(&self, seq_type: TypeTerm) -> Option< GenericReprTreeMorphism > {
+        self.into_list_map_dyn(seq_type)
     }
 }
 
@@ -54,7 +60,7 @@ impl GenericReprTreeMorphism {
         }
     }
 
-    pub fn into_list_map< SrcItem, DstItem >(&self, list_typeid: TypeID)
+    pub fn into_list_map< SrcItem, DstItem >(&self, seq_type: TypeTerm)
     -> GenericReprTreeMorphism
     where
         SrcItem: Clone + Send + Sync + 'static,
@@ -62,11 +68,11 @@ impl GenericReprTreeMorphism {
     {
         let mut lst_map_type = MorphismType {
             src_type: TypeTerm::App(vec![
-                TypeTerm::TypeID(list_typeid),
+                seq_type.clone(),
                 self.morph_type.src_type.clone()
             ]),
             dst_type: TypeTerm::App(vec![
-                TypeTerm::TypeID(list_typeid),
+                seq_type.clone(),
                 self.morph_type.dst_type.clone()
             ])
         }.normalize();
@@ -86,14 +92,13 @@ impl GenericReprTreeMorphism {
                     "lst map type ::\n {:?}\n===>  {:?}\n\n", lst_map_type.src_type, lst_map_type.dst_type
                 );
 
-                
                 let mut item_ladder = item_morph.morph_type.src_type.clone().get_lnf_vec();
                 let top_type = item_ladder.remove( item_ladder.len() - 1 );
 
                 if let Ok(item_sigma) = laddertypes::unify(
                     &top_type,
                     &TypeTerm::App(vec![
-                        TypeTerm::TypeID( list_typeid ),
+                        seq_type.clone(),
                         TypeTerm::TypeID( TypeID::Var( 200 ) )
                     ])
                 ) {
@@ -113,7 +118,7 @@ impl GenericReprTreeMorphism {
                                     top_type.clone(),
                                     r3vi::buffer::singleton::SingletonBuffer::new(x.clone())
                             );
-                            
+
 
                             // TODO: required?
                             for t in item_ladder.iter().rev() {
@@ -139,43 +144,43 @@ impl GenericReprTreeMorphism {
         }
     }
 
-    pub fn into_list_map_dyn(&self, typeid_list: TypeID)
+    pub fn into_list_map_dyn(&self, seq_type: TypeTerm)
     -> Option< GenericReprTreeMorphism >
-    {        
+    {
         let src_item_type_lnf = self.morph_type.src_type.clone().get_lnf_vec();
         let dst_item_type_lnf = self.morph_type.dst_type.clone().get_lnf_vec();
 
-        eprintln!("into list map dyn");
+        eprintln!("into list map dyn:\n src {:?}\n dst {:?}", src_item_type_lnf, dst_item_type_lnf);
 
         if src_item_type_lnf.last() == Some(&TypeTerm::TypeID(TYPEID_char)) &&
            dst_item_type_lnf.last() == Some(&TypeTerm::TypeID(TYPEID_char))
         {
-            Some( self.into_list_map::< char, char >(TYPEID_list) )
+            Some( self.into_list_map::< char, char >( seq_type ) )
         }
         else if src_item_type_lnf.last() == Some(&TypeTerm::TypeID(TYPEID_u64)) &&
            dst_item_type_lnf.last() == Some(&TypeTerm::TypeID(TYPEID_u64))
         {
-            Some( self.into_list_map::< u64, u64 >(TYPEID_list) )
+            Some( self.into_list_map::< u64, u64 >( seq_type ) )
         }
         else if src_item_type_lnf.last() == Some(&TypeTerm::TypeID(TYPEID_char)) &&
            dst_item_type_lnf.last() == Some(&TypeTerm::TypeID(TYPEID_u64))
         {
-            Some( self.into_list_map::< char, u64 >(TYPEID_list) )
+            Some( self.into_list_map::< char, u64 >( seq_type ) )
         }
         else if src_item_type_lnf.last() == Some(&TypeTerm::TypeID(TYPEID_u64)) &&
                 dst_item_type_lnf.last() == Some(&TypeTerm::TypeID(TYPEID_char))
         {
-            Some( self.into_list_map::< u64, char >(TYPEID_list) )
+            Some( self.into_list_map::< u64, char >( seq_type ) )
         }
         else if src_item_type_lnf.last() == Some(&TypeTerm::TypeID(TYPEID_char)) &&
                 dst_item_type_lnf.last() == Some(&TypeTerm::TypeID(TYPEID_edittree))
         {
-            Some( self.into_list_map::< char, Arc<RwLock<crate::edit_tree::EditTree>> >(TYPEID_list) )
+            Some( self.into_list_map::< char, Arc<RwLock<crate::edit_tree::EditTree>> >(seq_type) )
         }
         else if src_item_type_lnf.last() == Some(&TypeTerm::TypeID(TYPEID_edittree)) &&
                 dst_item_type_lnf.last() == Some(&TypeTerm::TypeID(TYPEID_char))
         {
-            Some( self.into_list_map::< Arc<RwLock<crate::edit_tree::EditTree>>, char >(TYPEID_list) )
+            Some( self.into_list_map::< Arc<RwLock<crate::edit_tree::EditTree>>, char >(seq_type) )
         }
 /*
         else if src_item_type_lnf.last() == Some(&TypeTerm::App(vec![ TypeTerm::TypeID(typeid_list), TypeTerm::TypeID(typeid_char) ])) &&
@@ -208,4 +213,3 @@ impl GenericReprTreeMorphism {
 }
 
 //<<<<>>>><<>><><<>><<<*>>><<>><><<>><<<<>>>>
-