diff --git a/src/flow/binary.rs b/src/flow/binary.rs
index 394e2a1..fb704a7 100644
--- a/src/flow/binary.rs
+++ b/src/flow/binary.rs
@@ -23,14 +23,18 @@ pub trait BinaryTrees: Clone {
     type Reference: Send;
     type Tree: Send;
     type Key: Send + Clone;
-    type Comparator: Comparator<Self::Key>;
 
-    fn comparator(&self) -> &Self::Comparator;
     fn split(&self, node: &Self::Node) -> Split<Self>;
     fn equal(&self, rl: &Self::Reference, rr: &Self::Reference) -> bool;
     fn refer(&self, tree: &Self::Tree) -> Option<Self::Reference>;
 }
 
+pub trait WithComparator: BinaryTrees {
+    type Comparator: Comparator<Self::Key>;
+
+    fn comparator(&self) -> &Self::Comparator;
+}
+
 pub trait MonadTrees<'a>: MonadContext<'a> + BinaryTrees {
     fn resolve(&self, reference: &Self::Reference) -> BTWrap<'a, Self, Self::Node>;
 }
@@ -50,7 +54,9 @@ pub trait BinaryTreesEmpty<'a>: MonadTrees<'a> {
         -> BTWrap<'a, Self, KeySplit<Self>>;
 }
 
-pub trait BinaryTreesMutable<'a>: BinaryTreesEmpty<'a> + BinaryTreesTreeOf<'a> {
+pub trait BinaryTreesMutable<'a>:
+    BinaryTreesEmpty<'a> + BinaryTreesTreeOf<'a> + WithComparator
+{
     fn join_key(
         self,
         tl: Self::Tree,
diff --git a/src/flow/binary/balancing.rs b/src/flow/binary/balancing.rs
index 87539c2..1830e2d 100644
--- a/src/flow/binary/balancing.rs
+++ b/src/flow/binary/balancing.rs
@@ -84,16 +84,19 @@ fn matches_height(hl: u64, hr: u64, hp: u64) -> Result<(), BalancingError> {
     }
 }
 
-impl<BT: TreesHeight> BinaryTrees for BalancedTrees<BT> {
-    type Node = BT::Node;
-    type Reference = (BT::Reference, u64);
-    type Tree = BT::Tree;
-    type Key = BT::Key;
+impl<BT: TreesHeight + WithComparator> WithComparator for BalancedTrees<BT> {
     type Comparator = BT::Comparator;
 
     fn comparator(&self) -> &Self::Comparator {
         self.0.comparator()
     }
+}
+
+impl<BT: TreesHeight> BinaryTrees for BalancedTrees<BT> {
+    type Node = BT::Node;
+    type Reference = (BT::Reference, u64);
+    type Tree = BT::Tree;
+    type Key = BT::Key;
 
     fn split(&self, node: &Self::Node) -> Split<Self> {
         self.0.split(node)
@@ -108,7 +111,10 @@ impl<BT: TreesHeight> BinaryTrees for BalancedTrees<BT> {
     }
 }
 
-impl<'a, BT: BinaryTreesUnbalanced<'a>> MonadTrees<'a> for BalancedTrees<BT> {
+impl<'a, BT> MonadTrees<'a> for BalancedTrees<BT>
+where
+    BT: BinaryTreesUnbalanced<'a>,
+{
     fn resolve(&self, (reference, hp): &Self::Reference) -> BTWrap<'a, Self, Self::Node> {
         let hp = *hp;
         let ctx = self.0.clone();
@@ -119,7 +125,10 @@ impl<'a, BT: BinaryTreesUnbalanced<'a>> MonadTrees<'a> for BalancedTrees<BT> {
     }
 }
 
-impl<'a, BT: BinaryTreesUnbalanced<'a>> BinaryTreesTreeOf<'a> for BalancedTrees<BT> {
+impl<'a, BT> BinaryTreesTreeOf<'a> for BalancedTrees<BT>
+where
+    BT: BinaryTreesUnbalanced<'a>,
+{
     fn tree_of(&self, node: Self::Node) -> BTWrap<'a, Self, Self::Tree> {
         let (hl, hr) = self.0.node_heights(&node);
         self.0.balancing_bind(parent_height(hl, hr), |height| {
@@ -128,8 +137,9 @@ impl<'a, BT: BinaryTreesUnbalanced<'a>> BinaryTreesTreeOf<'a> for BalancedTrees<
     }
 }
 
-impl<'a, BT: BinaryTreesUnbalanced<'a> + BinaryTreesEmpty<'a>> BinaryTreesEmpty<'a>
-    for BalancedTrees<BT>
+impl<'a, BT> BinaryTreesEmpty<'a> for BalancedTrees<BT>
+where
+    BT: BinaryTreesUnbalanced<'a> + BinaryTreesEmpty<'a>,
 {
     fn empty(&self) -> Self::Tree {
         self.0.empty()
@@ -150,14 +160,18 @@ impl<BT: TreesHeight> TreesHeight for BalancedTrees<BT> {
     }
 }
 
-impl<'a, BT: BinaryTreesUnbalanced<'a>> TreesHeightError<'a> for BalancedTrees<BT> {
+impl<'a, BT> TreesHeightError<'a> for BalancedTrees<BT>
+where
+    BT: BinaryTreesUnbalanced<'a>,
+{
     fn height_error<T: 'a + Send>(&self, error: HeightError) -> BTWrap<'a, Self, T> {
         self.0.height_error(error)
     }
 }
 
-impl<'a, BT: BinaryTreesUnbalanced<'a> + BinaryTreesTryJoin<'a>> BinaryTreesTryJoin<'a>
-    for BalancedTrees<BT>
+impl<'a, BT> BinaryTreesTryJoin<'a> for BalancedTrees<BT>
+where
+    BT: BinaryTreesUnbalanced<'a> + BinaryTreesTryJoin<'a>,
 {
     fn try_join(
         &self,
@@ -171,8 +185,9 @@ impl<'a, BT: BinaryTreesUnbalanced<'a> + BinaryTreesTryJoin<'a>> BinaryTreesTryJ
     }
 }
 
-impl<'a, BT: BinaryTreesUnbalanced<'a> + BinaryTreesBindable<'a>> BinaryTreesBindable<'a>
-    for BalancedTrees<BT>
+impl<'a, BT> BinaryTreesBindable<'a> for BalancedTrees<BT>
+where
+    BT: BinaryTreesUnbalanced<'a> + BinaryTreesBindable<'a>,
 {
     fn bounds_error<T: 'a + Send>(
         &self,
@@ -182,8 +197,9 @@ impl<'a, BT: BinaryTreesUnbalanced<'a> + BinaryTreesBindable<'a>> BinaryTreesBin
     }
 }
 
-impl<'a, BT: BinaryTreesUnbalanced<'a> + BinaryTreesEmpty<'a> + BinaryTreesTryJoin<'a>>
-    BinaryTreesMutable<'a> for BalancedTrees<BT>
+impl<'a, BT> BinaryTreesMutable<'a> for BalancedTrees<BT>
+where
+    BT: BinaryTreesUnbalanced<'a> + BinaryTreesEmpty<'a> + BinaryTreesTryJoin<'a> + WithComparator,
 {
     fn join_key(
         self,
diff --git a/src/flow/binary/bound.rs b/src/flow/binary/bound.rs
index 2903595..1629e78 100644
--- a/src/flow/binary/bound.rs
+++ b/src/flow/binary/bound.rs
@@ -58,16 +58,19 @@ pub trait BinaryTreesBindable<'a>: MonadTrees<'a> {
     }
 }
 
-impl<BT: BinaryTrees> BinaryTrees for BoundTrees<BT> {
-    type Node = BoundNode<Self::Key, BT::Node>;
-    type Reference = Bound<Self::Key, BT::Reference>;
-    type Tree = Bound<Self::Key, BT::Tree>;
-    type Key = BT::Key;
+impl<BT: WithComparator> WithComparator for BoundTrees<BT> {
     type Comparator = BT::Comparator;
 
     fn comparator(&self) -> &Self::Comparator {
         self.0.comparator()
     }
+}
+
+impl<BT: WithComparator> BinaryTrees for BoundTrees<BT> {
+    type Node = BoundNode<Self::Key, BT::Node>;
+    type Reference = Bound<Self::Key, BT::Reference>;
+    type Tree = Bound<Self::Key, BT::Tree>;
+    type Key = BT::Key;
 
     fn split(&self, node: &Self::Node) -> Split<Self> {
         let (tl, tr, key) = self.0.split(&node.node);
@@ -97,7 +100,10 @@ impl<BT: BinaryTrees> BinaryTrees for BoundTrees<BT> {
     }
 }
 
-impl<'a, BT: BinaryTreesBindable<'a>> MonadTrees<'a> for BoundTrees<BT> {
+impl<'a, BT> MonadTrees<'a> for BoundTrees<BT>
+where
+    BT: BinaryTreesBindable<'a> + WithComparator,
+{
     fn resolve(&self, reference: &Self::Reference) -> BTWrap<'a, Self, Self::Node> {
         let ctx = self.0.clone();
         let bounds = reference.bounds.clone();
@@ -118,8 +124,9 @@ impl<'a, BT: BinaryTreesBindable<'a>> MonadTrees<'a> for BoundTrees<BT> {
     }
 }
 
-impl<'a, BT: BinaryTreesBindable<'a> + BinaryTreesTreeOf<'a>> BinaryTreesTreeOf<'a>
-    for BoundTrees<BT>
+impl<'a, BT> BinaryTreesTreeOf<'a> for BoundTrees<BT>
+where
+    BT: BinaryTreesBindable<'a> + BinaryTreesTreeOf<'a> + WithComparator,
 {
     fn tree_of(&self, node: Self::Node) -> BTWrap<'a, Self, Self::Tree> {
         Self::fmap(self.0.tree_of(node.node), move |tree| Bound {
@@ -129,8 +136,9 @@ impl<'a, BT: BinaryTreesBindable<'a> + BinaryTreesTreeOf<'a>> BinaryTreesTreeOf<
     }
 }
 
-impl<'a, BT: BinaryTreesBindable<'a> + BinaryTreesEmpty<'a>> BinaryTreesEmpty<'a>
-    for BoundTrees<BT>
+impl<'a, BT> BinaryTreesEmpty<'a> for BoundTrees<BT>
+where
+    BT: BinaryTreesBindable<'a> + BinaryTreesEmpty<'a> + WithComparator,
 {
     fn empty(&self) -> Self::Tree {
         Bound {
@@ -164,22 +172,24 @@ impl<'a, BT: BinaryTreesBindable<'a> + BinaryTreesEmpty<'a>> BinaryTreesEmpty<'a
     }
 }
 
-impl<BT: TreesHeight> TreesHeight for BoundTrees<BT> {
+impl<BT: TreesHeight + WithComparator> TreesHeight for BoundTrees<BT> {
     fn height(&self, tree: &Self::Tree) -> u64 {
         self.0.height(&tree.bound)
     }
 }
 
-impl<'a, BT: BinaryTreesBindable<'a> + TreesHeightError<'a>> TreesHeightError<'a>
-    for BoundTrees<BT>
+impl<'a, BT> TreesHeightError<'a> for BoundTrees<BT>
+where
+    BT: BinaryTreesBindable<'a> + TreesHeightError<'a> + WithComparator,
 {
     fn height_error<T: 'a + Send>(&self, error: HeightError) -> BTWrap<'a, Self, T> {
         self.0.height_error(error)
     }
 }
 
-impl<'a, BT: BinaryTreesBindable<'a> + BinaryTreesTryJoin<'a>> BinaryTreesTryJoin<'a>
-    for BoundTrees<BT>
+impl<'a, BT> BinaryTreesTryJoin<'a> for BoundTrees<BT>
+where
+    BT: BinaryTreesBindable<'a> + BinaryTreesTryJoin<'a> + WithComparator,
 {
     fn try_join(
         &self,
@@ -202,14 +212,14 @@ impl<'a, BT: BinaryTreesBindable<'a> + BinaryTreesTryJoin<'a>> BinaryTreesTryJoi
     }
 }
 
-impl<
-        'a,
-        BT: BinaryTreesBindable<'a>
-            + BinaryTreesTreeOf<'a>
-            + BinaryTreesEmpty<'a>
-            + TreesHeightError<'a>
-            + BinaryTreesTryJoin<'a>,
-    > BinaryTreesMutable<'a> for BoundTrees<BT>
+impl<'a, BT> BinaryTreesMutable<'a> for BoundTrees<BT>
+where
+    BT: BinaryTreesBindable<'a>
+        + BinaryTreesTreeOf<'a>
+        + BinaryTreesEmpty<'a>
+        + TreesHeightError<'a>
+        + BinaryTreesTryJoin<'a>
+        + WithComparator,
 {
     fn join_key(
         self,
diff --git a/src/mrds/trees/heighted.rs b/src/mrds/trees/heighted.rs
index 2fd7e9a..65b7cbf 100644
--- a/src/mrds/trees/heighted.rs
+++ b/src/mrds/trees/heighted.rs
@@ -86,16 +86,19 @@ impl<'a, A: 'a + Send> FunctorContext<'a> for Trees<A> {
     type T = instances::solo::SoloInstance;
 }
 
-impl<A: Send + Sync + Ord + Clone> BinaryTrees for Trees<A> {
-    type Node = Node<A>;
-    type Reference = Reference<A>;
-    type Tree = Tree<A>;
-    type Key = A;
+impl<A: Send + Sync + Ord + Clone> WithComparator for Trees<A> {
     type Comparator = DefaultComparator;
 
     fn comparator(&self) -> &Self::Comparator {
         &DefaultComparator
     }
+}
+
+impl<A: Send + Sync + Ord + Clone> BinaryTrees for Trees<A> {
+    type Node = Node<A>;
+    type Reference = Reference<A>;
+    type Tree = Tree<A>;
+    type Key = A;
 
     fn split(&self, node: &Self::Node) -> Split<Self> {
         (node.l.clone(), node.r.clone(), node.key.clone())
diff --git a/src/rstd/collections/tree/context.rs b/src/rstd/collections/tree/context.rs
index 476212a..4beabad 100644
--- a/src/rstd/collections/tree/context.rs
+++ b/src/rstd/collections/tree/context.rs
@@ -69,6 +69,21 @@ impl<
     type T = FallibleMonad<'a, Ctx, TreeContextError<'a, Ctx, A, E>>;
 }
 
+impl<
+        'a,
+        Ctx: Context<'a>,
+        A: Mentionable<'a, Ctx> + Clone,
+        C: 'a + Comparator<A>,
+        E: 'a + Send,
+    > WithComparator for TreeContext2<'a, Ctx, A, C, E>
+{
+    type Comparator = C;
+
+    fn comparator(&self) -> &Self::Comparator {
+        self.0 .0.as_ref()
+    }
+}
+
 impl<
         'a,
         Ctx: Context<'a>,
@@ -81,11 +96,6 @@ impl<
     type Reference = Point<'a, Ctx, Self::Node>;
     type Tree = Tree<'a, Ctx, A>;
     type Key = A;
-    type Comparator = C;
-
-    fn comparator(&self) -> &Self::Comparator {
-        self.0 .0.as_ref()
-    }
 
     fn split(&self, node: &Self::Node) -> crate::flow::binary::Split<Self> {
         (node.l.clone(), node.r.clone(), node.key.clone())