diff --git a/nested/src/char_editor.rs b/nested/src/char_editor.rs
index 89a92e9..8a1e22d 100644
--- a/nested/src/char_editor.rs
+++ b/nested/src/char_editor.rs
@@ -1,6 +1,7 @@
 use {
     crate::{
-        core::{OuterViewPort, Context},
+        core::{OuterViewPort},
+        type_system::{Context},
         singleton::{SingletonBuffer, SingletonView},
         terminal::{TerminalAtom, TerminalEvent, TerminalStyle},
         tree::NestedNode, Commander
diff --git a/nested/src/core/mod.rs b/nested/src/core/mod.rs
index 18c63a9..fb89afb 100644
--- a/nested/src/core/mod.rs
+++ b/nested/src/core/mod.rs
@@ -1,17 +1,12 @@
 pub mod channel;
-pub mod context;
 pub mod observer;
 pub mod port;
-pub mod type_term;
 pub mod view;
 
 pub use {
     channel::{queue_channel, set_channel, singleton_channel, ChannelReceiver, ChannelSender},
-    context::{Context, MorphismMode, MorphismType, ReprTree},
     observer::{NotifyFnObserver, Observer, ObserverBroadcast, ObserverExt, ResetFnObserver},
-    port::{
-        AnyInnerViewPort, AnyOuterViewPort, AnyViewPort, InnerViewPort, OuterViewPort, ViewPort,
-    },
-    type_term::{TypeDict, TypeID, TypeTerm, TypeLadder},
-    view::View,
+    port::{AnyInnerViewPort, AnyOuterViewPort, AnyViewPort, InnerViewPort, OuterViewPort, ViewPort},
+    view::View
 };
+
diff --git a/nested/src/integer/editor.rs b/nested/src/integer/editor.rs
index ccc6307..6d99f57 100644
--- a/nested/src/integer/editor.rs
+++ b/nested/src/integer/editor.rs
@@ -1,6 +1,7 @@
 use {
     crate::{
-        core::{OuterViewPort, Context, TypeTerm},
+        core::{OuterViewPort},
+        type_system::{Context, TypeTerm},
         list::{PTYListEditor},
         sequence::{SequenceView, SequenceViewExt, decorator::{PTYSeqDecorate, SeqDecorStyle}},
         singleton::{SingletonBuffer, SingletonView},
diff --git a/nested/src/lib.rs b/nested/src/lib.rs
index afcd3dc..0ed80a3 100644
--- a/nested/src/lib.rs
+++ b/nested/src/lib.rs
@@ -2,11 +2,13 @@
 
 // general
 pub mod core;
+pub mod type_system;
 pub mod projection;
 pub mod bimap;
 pub mod modulo;
 pub use modulo::modulo;
 
+
 // semantics
 pub mod singleton;
 pub mod sequence;
@@ -45,7 +47,7 @@ pub trait Commander {
 
 use std::sync::{Arc, RwLock};
 use crate::{
-    core::context::ReprTree,
+    type_system::ReprTree,
     singleton::SingletonView
 };
 
diff --git a/nested/src/list/editor.rs b/nested/src/list/editor.rs
index d97e883..6f38e2e 100644
--- a/nested/src/list/editor.rs
+++ b/nested/src/list/editor.rs
@@ -1,6 +1,7 @@
 use {
     crate::{
-        core::{OuterViewPort, ViewPort, Context, TypeTerm},
+        core::{OuterViewPort, ViewPort},
+        type_system::{Context, TypeTerm},
         list::{
             ListCursor,
             ListSegment,
diff --git a/nested/src/list/pty_editor.rs b/nested/src/list/pty_editor.rs
index c85c43f..cc499c3 100644
--- a/nested/src/list/pty_editor.rs
+++ b/nested/src/list/pty_editor.rs
@@ -1,6 +1,7 @@
 use {
     crate::{
-        core::{OuterViewPort, Context, TypeTerm},
+        core::{OuterViewPort},
+        type_system::{Context, TypeTerm},
         list::{
             ListCursor, ListCursorMode,
             ListEditor
diff --git a/nested/src/make_editor.rs b/nested/src/make_editor.rs
index 1425edb..ee7378b 100644
--- a/nested/src/make_editor.rs
+++ b/nested/src/make_editor.rs
@@ -1,6 +1,6 @@
 use {
     crate::{
-        core::{TypeTerm, Context},
+        type_system::{TypeTerm, Context},
         integer::{DigitEditor, PosIntEditor},
         list::{PTYListEditor},
         sequence::{decorator::{SeqDecorStyle}},
@@ -12,6 +12,14 @@ use {
     std::sync::{Arc, RwLock},
 };
 
+pub fn init_mem_ctx(parent: Arc<RwLock<Context>>) -> Arc<RwLock<Context>> {
+    let ctx = Arc::new(RwLock::new(Context::with_parent(Some(parent))));
+
+    ctx.write().unwrap().add_typename("Vec".into());
+
+    ctx
+}
+
 pub fn init_editor_ctx(parent: Arc<RwLock<Context>>) -> Arc<RwLock<Context>> {
     let ctx = Arc::new(RwLock::new(Context::with_parent(Some(parent))));
 
diff --git a/nested/src/product/editor.rs b/nested/src/product/editor.rs
index be50901..4ea4bbb 100644
--- a/nested/src/product/editor.rs
+++ b/nested/src/product/editor.rs
@@ -1,6 +1,7 @@
 use {
     crate::{
-        core::{OuterViewPort, TypeLadder, Context},
+        core::{OuterViewPort},
+        type_system::{TypeLadder, Context},
         terminal::{
             TerminalEditor, TerminalEditorResult,
             TerminalEvent, TerminalView
diff --git a/nested/src/product/nav.rs b/nested/src/product/nav.rs
index 1e8ce9d..01456e4 100644
--- a/nested/src/product/nav.rs
+++ b/nested/src/product/nav.rs
@@ -1,6 +1,6 @@
 use {
     crate::{
-        core::Context,
+        type_system::Context,
         list::ListCursorMode,
         tree::{TreeNav, TreeNavResult, TreeCursor},
         product::{segment::ProductEditorSegment, ProductEditor},
diff --git a/nested/src/product/segment.rs b/nested/src/product/segment.rs
index 395755c..30d4851 100644
--- a/nested/src/product/segment.rs
+++ b/nested/src/product/segment.rs
@@ -1,6 +1,7 @@
 use {
     crate::{
-        core::{OuterViewPort, TypeLadder, Context},
+        core::{OuterViewPort},
+        type_system::{TypeLadder, Context},
         terminal::{
             TerminalStyle, TerminalView,
             make_label
diff --git a/nested/src/tree/node.rs b/nested/src/tree/node.rs
index 35652da..07a3edb 100644
--- a/nested/src/tree/node.rs
+++ b/nested/src/tree/node.rs
@@ -2,7 +2,8 @@ use {
     std::sync::{Arc, RwLock},
     cgmath::Vector2,
     crate::{
-        core::{ViewPort, OuterViewPort, AnyOuterViewPort, context::ReprTree, Context},
+        core::{ViewPort, OuterViewPort, AnyOuterViewPort},
+        type_system::{ReprTree, Context},
         singleton::{SingletonBuffer},
         sequence::SequenceView,
         terminal::{TerminalView, TerminalEvent, TerminalEditor, TerminalEditorResult},
@@ -16,6 +17,8 @@ use {
 #[derive(Clone)]
 pub struct NestedNode {
     pub ctx: Option<Arc<RwLock<Context>>>,
+
+//    pub abs: Option<Arc<RwLock<ReprTree>>>,
     pub view: Option<OuterViewPort<dyn TerminalView>>,
     pub diag: Option<OuterViewPort<dyn SequenceView<Item = Message>>>,
     pub cmd: Option<Arc<RwLock<dyn ObjCommander + Send + Sync>>>,
@@ -50,7 +53,6 @@ impl TerminalEditor for NestedNode {
     }
 }
 
-
 impl TreeNav for NestedNode {
     fn get_cursor(&self) -> TreeCursor {
         if let Some(tn) = self.tree_nav.as_ref() {
diff --git a/nested/src/core/context.rs b/nested/src/type_system/context.rs
similarity index 52%
rename from nested/src/core/context.rs
rename to nested/src/type_system/context.rs
index 3d463e8..779d0e6 100644
--- a/nested/src/core/context.rs
+++ b/nested/src/type_system/context.rs
@@ -1,214 +1,17 @@
 use {
     crate::{
-        core::{
-            type_term::{TypeDict, TypeTerm, TypeID},
-            AnyOuterViewPort, OuterViewPort, View,
-        },
+        core::{AnyOuterViewPort, OuterViewPort, View},
+        type_system::{TypeDict, TypeTerm, TypeID, ReprTree},
         tree::NestedNode
     },
     std::{
         collections::HashMap,
         sync::{Arc, RwLock},
-    },
+    }
 };
 
 //<<<<>>>><<>><><<>><<<*>>><<>><><<>><<<<>>>>
 
-#[derive(Clone)]
-pub struct ReprTree {
-    type_tag: TypeTerm,
-    port: Option<AnyOuterViewPort>,
-    branches: HashMap<TypeTerm, Arc<RwLock<ReprTree>>>,
-}
-
-impl ReprTree {
-    pub fn new(type_tag: TypeTerm) -> Self {
-        ReprTree {
-            type_tag,
-            port: None,
-            branches: HashMap::new(),
-        }
-    }
-
-    pub fn new_leaf(type_tag: TypeTerm, port: AnyOuterViewPort) -> Arc<RwLock<Self>> {
-        let mut tree = ReprTree::new(type_tag);
-        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 get_port<V: View + ?Sized + 'static>(&self) -> Option<OuterViewPort<V>>
-    where
-        V::Msg: Clone,
-    {
-        Some(
-            self.port
-                .clone()?
-                .downcast::<V>()
-                .ok()
-                .unwrap()
-        )
-    }
-
-    pub fn get_view<V: View + ?Sized + 'static>(&self) -> Option<Arc<V>>
-    where
-        V::Msg: Clone,
-    {
-            self.get_port::<V>()?
-                .get_view()
-    }
-
-    // descend
-    pub fn downcast(&self, dst_type: &TypeTerm) -> Option<Arc<RwLock<ReprTree>>> {
-        self.branches.get(dst_type).cloned()
-    }
-
-    pub fn downcast_ladder(&self, mut repr_ladder: impl Iterator<Item = TypeTerm>) -> Option<Arc<RwLock<ReprTree>>> {
-        let first = repr_ladder.next()?;
-        repr_ladder.fold(
-            self.downcast(&first),
-            |s, t| s?.read().unwrap().downcast(&t))
-    }
-
-    // ascend
-    pub fn upcast(rt: &Arc<RwLock<Self>>, type_term: TypeTerm) -> Arc<RwLock<ReprTree>> {
-        let mut n = Self::new(type_term);
-        n.insert_branch(rt.clone());
-        Arc::new(RwLock::new(n))
-    }
-
-/*
-    pub fn add_iso_repr(
-        &self,
-        type_ladder: impl Iterator<Item = TypeTerm>,
-        morphism_constructors: &HashMap<MorphismType, Box<dyn Fn(Object) -> Object>>,
-    ) {
-        let mut cur_repr = self.repr.clone();
-
-        for dst_type in type_ladder {
-            if let Some(next_repr) = self.repr.read().unwrap().branches.get(&dst_type) {
-                // go deeper
-                cur_repr = next_repr.clone();
-            } else {
-                // search for morphism constructor and insert new repr
-                let mut obj = None;
-
-                for src_type in cur_repr.read().unwrap().branches.keys() {
-                    if let Some(ctor) = morphism_constructors.get(&MorphismType {
-                        mode: MorphismMode::Iso,
-                        src_type: src_type.clone(),
-                        dst_type: dst_type.clone(),
-                    }) {
-                        let new_obj = ctor(Object {
-                            type_tag: src_type.clone(),
-                            repr: cur_repr
-                                .read()
-                                .unwrap()
-                                .branches
-                                .get(&src_type)
-                                .unwrap()
-                                .clone(),
-                        });
-
-                        assert!(new_obj.type_tag == dst_type);
-
-                        obj = Some(new_obj);
-                        break;
-                    }
-                }
-
-                if let Some(obj) = obj {
-                    cur_repr
-                        .write()
-                        .unwrap()
-                        .insert_branch(obj.type_tag, obj.repr);
-                } else {
-                    panic!("could not find matching isomorphism!");
-                }
-            }
-        }
-    }
-
-    pub fn add_mono_repr<'a>(
-        &self,
-        type_ladder: impl Iterator<Item = TypeTerm>,
-        morphism_constructors: &HashMap<MorphismType, Box<dyn Fn(Object) -> Object>>,
-    ) {
-        let mut cur_type = self.type_tag.clone();
-        let mut cur_repr = self.repr.clone();   
-
-        for dst_type in type_ladder {
-            if let Some(next_repr) = self.repr.read().unwrap().branches.get(&dst_type) {
-                // go deeper
-                cur_type = dst_type;
-                cur_repr = next_repr.clone();
-            } else {
-                if let Some(constructor) = morphism_constructors.get(&MorphismType {
-                    mode: MorphismMode::Mono,
-                    src_type: cur_type.clone(),
-                    dst_type: dst_type.clone(),
-                }) {
-                    let new_obj = constructor(Object {
-                        type_tag: cur_type.clone(),
-                        repr: cur_repr
-                            .read()
-                            .unwrap()
-                            .branches
-                            .get(&cur_type)
-                            .unwrap()
-                            .clone(),
-                    });
-
-                    assert!(new_obj.type_tag == dst_type);
-                    cur_repr
-                        .write()
-                        .unwrap()
-                        .insert_branch(new_obj.type_tag.clone(), new_obj.repr.clone());
-
-                    cur_type = new_obj.type_tag;
-                    cur_repr = new_obj.repr;
-                }
-            }
-        }
-    }
-
-    // replace with higher-level type in which self is a repr branch
-    pub fn epi_cast<'a>(
-        &self,
-        _type_ladder: impl Iterator<Item = TypeTerm>,
-        _morphism_constructors: &HashMap<MorphismType, Box<dyn Fn(Object) -> Object>>,
-    ) {
-        // todo
-        
-}
-    */
-}
-
-//<<<<>>>><<>><><<>><<<*>>><<>><><<>><<<<>>>>
-
 pub struct TypeLadder(Vec<TypeTerm>);
 
 #[derive(Clone, Copy, Hash, PartialEq, Eq)]
diff --git a/nested/src/type_system/mod.rs b/nested/src/type_system/mod.rs
new file mode 100644
index 0000000..72e2db3
--- /dev/null
+++ b/nested/src/type_system/mod.rs
@@ -0,0 +1,10 @@
+pub mod type_term;
+pub mod repr_tree;
+pub mod context;
+
+pub use {
+    repr_tree::{ReprTree},
+    type_term::{TypeDict, TypeID, TypeTerm, TypeLadder},
+    context::{Context, MorphismMode, MorphismType},
+};
+
diff --git a/nested/src/type_system/repr_tree.rs b/nested/src/type_system/repr_tree.rs
new file mode 100644
index 0000000..cd1d046
--- /dev/null
+++ b/nested/src/type_system/repr_tree.rs
@@ -0,0 +1,205 @@
+use {
+    crate::{
+        core::{AnyOuterViewPort, OuterViewPort, View},
+        type_system::{TypeDict, TypeTerm, TypeID},
+        tree::NestedNode
+    },
+    std::{
+        collections::HashMap,
+        sync::{Arc, RwLock},
+    },
+};
+
+//<<<<>>>><<>><><<>><<<*>>><<>><><<>><<<<>>>>
+
+#[derive(Clone)]
+pub struct ReprTree {
+    type_tag: TypeTerm,
+    port: Option<AnyOuterViewPort>,
+    branches: HashMap<TypeTerm, Arc<RwLock<ReprTree>>>,
+}
+
+impl ReprTree {
+    pub fn new(type_tag: TypeTerm) -> Self {
+        ReprTree {
+            type_tag,
+            port: None,
+            branches: HashMap::new(),
+        }
+    }
+
+    pub fn new_leaf(type_tag: TypeTerm, port: AnyOuterViewPort) -> Arc<RwLock<Self>> {
+        let mut tree = ReprTree::new(type_tag);
+        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 get_port<V: View + ?Sized + 'static>(&self) -> Option<OuterViewPort<V>>
+    where
+        V::Msg: Clone,
+    {
+        Some(
+            self.port
+                .clone()?
+                .downcast::<V>()
+                .ok()
+                .unwrap()
+        )
+    }
+
+    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: &TypeTerm) -> Option<Arc<RwLock<ReprTree>>> {
+        self.branches.get(dst_type).cloned()
+    }
+
+    pub fn descend_ladder(&self, mut repr_ladder: impl Iterator<Item = TypeTerm>) -> Option<Arc<RwLock<ReprTree>>> {
+        let first = repr_ladder.next()?;
+        repr_ladder.fold(
+            self.descend(&first),
+            |s, t| s?.read().unwrap().descend(&t))
+    }
+
+    pub fn ascend(rt: &Arc<RwLock<Self>>, type_term: TypeTerm) -> Arc<RwLock<ReprTree>> {
+        let mut n = Self::new(type_term);
+        n.insert_branch(rt.clone());
+        Arc::new(RwLock::new(n))
+    }
+
+/*
+    pub fn add_iso_repr(
+        &self,
+        type_ladder: impl Iterator<Item = TypeTerm>,
+        morphism_constructors: &HashMap<MorphismType, Box<dyn Fn(Object) -> Object>>,
+    ) {
+        let mut cur_repr = self.repr.clone();
+
+        for dst_type in type_ladder {
+            if let Some(next_repr) = self.repr.read().unwrap().branches.get(&dst_type) {
+                // go deeper
+                cur_repr = next_repr.clone();
+            } else {
+                // search for morphism constructor and insert new repr
+                let mut obj = None;
+
+                for src_type in cur_repr.read().unwrap().branches.keys() {
+                    if let Some(ctor) = morphism_constructors.get(&MorphismType {
+                        mode: MorphismMode::Iso,
+                        src_type: src_type.clone(),
+                        dst_type: dst_type.clone(),
+                    }) {
+                        let new_obj = ctor(Object {
+                            type_tag: src_type.clone(),
+                            repr: cur_repr
+                                .read()
+                                .unwrap()
+                                .branches
+                                .get(&src_type)
+                                .unwrap()
+                                .clone(),
+                        });
+
+                        assert!(new_obj.type_tag == dst_type);
+
+                        obj = Some(new_obj);
+                        break;
+                    }
+                }
+
+                if let Some(obj) = obj {
+                    cur_repr
+                        .write()
+                        .unwrap()
+                        .insert_branch(obj.type_tag, obj.repr);
+                } else {
+                    panic!("could not find matching isomorphism!");
+                }
+            }
+        }
+    }
+
+    pub fn add_mono_repr<'a>(
+        &self,
+        type_ladder: impl Iterator<Item = TypeTerm>,
+        morphism_constructors: &HashMap<MorphismType, Box<dyn Fn(Object) -> Object>>,
+    ) {
+        let mut cur_type = self.type_tag.clone();
+        let mut cur_repr = self.repr.clone();   
+
+        for dst_type in type_ladder {
+            if let Some(next_repr) = self.repr.read().unwrap().branches.get(&dst_type) {
+                // go deeper
+                cur_type = dst_type;
+                cur_repr = next_repr.clone();
+            } else {
+                if let Some(constructor) = morphism_constructors.get(&MorphismType {
+                    mode: MorphismMode::Mono,
+                    src_type: cur_type.clone(),
+                    dst_type: dst_type.clone(),
+                }) {
+                    let new_obj = constructor(Object {
+                        type_tag: cur_type.clone(),
+                        repr: cur_repr
+                            .read()
+                            .unwrap()
+                            .branches
+                            .get(&cur_type)
+                            .unwrap()
+                            .clone(),
+                    });
+
+                    assert!(new_obj.type_tag == dst_type);
+                    cur_repr
+                        .write()
+                        .unwrap()
+                        .insert_branch(new_obj.type_tag.clone(), new_obj.repr.clone());
+
+                    cur_type = new_obj.type_tag;
+                    cur_repr = new_obj.repr;
+                }
+            }
+        }
+    }
+
+    // replace with higher-level type in which self is a repr branch
+    pub fn epi_cast<'a>(
+        &self,
+        _type_ladder: impl Iterator<Item = TypeTerm>,
+        _morphism_constructors: &HashMap<MorphismType, Box<dyn Fn(Object) -> Object>>,
+    ) {
+        // todo
+        
+}
+    */
+}
+
diff --git a/nested/src/core/type_term.rs b/nested/src/type_system/type_term.rs
similarity index 100%
rename from nested/src/core/type_term.rs
rename to nested/src/type_system/type_term.rs
diff --git a/nested/src/type_term_editor.rs b/nested/src/type_term_editor.rs
index 19c555a..87eb5b9 100644
--- a/nested/src/type_term_editor.rs
+++ b/nested/src/type_term_editor.rs
@@ -1,6 +1,7 @@
 use {
     crate::{
-        core::{OuterViewPort, Context},
+        core::{OuterViewPort},
+        type_system::{Context},
         terminal::{TerminalEvent, TerminalView, TerminalEditor, TerminalEditorResult},
         sequence::{SequenceView, decorator::SeqDecorStyle},
         list::{PTYListEditor},
diff --git a/shell/src/main.rs b/shell/src/main.rs
index 0cf823e..b1c56c5 100644
--- a/shell/src/main.rs
+++ b/shell/src/main.rs
@@ -9,7 +9,8 @@ mod pty;
 use {
     cgmath::{Point2, Vector2},
     nested::{
-        core::{port::UpdateTask, Observer, AnyOuterViewPort, ViewPort, Context, ReprTree},
+        core::{port::UpdateTask, Observer, AnyOuterViewPort, ViewPort},
+        type_system::{Context, ReprTree},
         index::IndexArea,
         list::{ListCursorMode, PTYListEditor},
         sequence::{decorator::{SeqDecorStyle, Separate}},
@@ -54,19 +55,21 @@ async fn main() {
 
     // Type Context //
     let ctx = Arc::new(RwLock::new(Context::new()));
+    let ctx = nested::make_editor::init_mem_ctx(ctx);
     let ctx = nested::make_editor::init_editor_ctx(ctx);
     let ctx = nested::make_editor::init_math_ctx(ctx);
     let ctx = nested::make_editor::init_os_ctx(ctx);
 
     let vb = VecBuffer::<char>::new();
     let rt_char = ReprTree::new_leaf(
-        ctx.read().unwrap().type_term_from_str("( List Char 0 )").unwrap(),
+        ctx.read().unwrap().type_term_from_str("( Vec Char )").unwrap(),
         AnyOuterViewPort::from(vb.get_port())
     );
-    let rt_digit = ReprTree::upcast(&rt_char, ctx.read().unwrap().type_term_from_str("( List ( Digit 10 ) )").unwrap());
+
+    let rt_digit = ReprTree::ascend(&rt_char, ctx.read().unwrap().type_term_from_str("( List ( Digit 10 ) )").unwrap());
     rt_digit.write().unwrap().insert_branch(
         ReprTree::new_leaf(
-            ctx.read().unwrap().type_term_from_str("( List MachineInt )").unwrap(),
+            ctx.read().unwrap().type_term_from_str("( Vec MachineInt )").unwrap(),
             AnyOuterViewPort::from(
                 vb.get_port().to_sequence().map(
                     |c: &char| {
@@ -76,7 +79,7 @@ async fn main() {
             )
         )
     );
-    
+
 /*    
     ctx.write().unwrap().add_morphism(
         MorphismType{