diff --git a/src/flow/binary.rs b/src/flow/binary.rs
index 7ce3ac5..adde5ff 100644
--- a/src/flow/binary.rs
+++ b/src/flow/binary.rs
@@ -1,4 +1,5 @@
 mod avl;
+pub mod bounds;
 
 use crate::flow::comparator::*;
 use crate::func::{context::*, *};
diff --git a/src/flow/binary/bounds.rs b/src/flow/binary/bounds.rs
new file mode 100644
index 0000000..304f884
--- /dev/null
+++ b/src/flow/binary/bounds.rs
@@ -0,0 +1,82 @@
+use crate::flow::comparator::*;
+
+#[derive(Clone)]
+pub struct Bounds<A> {
+    l: Option<A>,
+    r: Option<A>,
+}
+
+pub enum BoundsError<A> {
+    BoundsViolated { l: A, r: A },
+    CannotJoin(A),
+}
+
+impl<A: Clone> Bounds<A> {
+    pub fn unbound() -> Self {
+        Bounds { l: None, r: None }
+    }
+
+    fn ordered(l: &A, r: &A, comparator: &impl Comparator<A>) -> Result<(), BoundsError<A>> {
+        if let Comparison::R = comparator.pick_smaller(l, r) {
+            Err(BoundsError::BoundsViolated {
+                l: l.clone(),
+                r: r.clone(),
+            })
+        } else {
+            Ok(())
+        }
+    }
+
+    fn new(
+        l: Option<A>,
+        r: Option<A>,
+        comparator: &impl Comparator<A>,
+    ) -> Result<Self, BoundsError<A>> {
+        if let (Some(kl), Some(kr)) = (&l, &r) {
+            Self::ordered(kl, kr, comparator)?
+        }
+        Ok(Bounds { l, r })
+    }
+
+    pub fn split(
+        self,
+        key: &A,
+        comparator: &impl Comparator<A>,
+    ) -> Result<(Self, Self), BoundsError<A>> {
+        Ok((
+            Self::new(self.l, Some(key.clone()), comparator)?,
+            Self::new(Some(key.clone()), self.r, comparator)?,
+        ))
+    }
+
+    pub fn join(
+        l: Self,
+        r: Self,
+        key: &A,
+        comparator: &impl Comparator<A>,
+    ) -> Result<Self, BoundsError<A>> {
+        if let Some(lr) = &l.r {
+            Self::ordered(lr, key, comparator)?
+        } else {
+            Err(BoundsError::CannotJoin(key.clone()))?
+        }
+        if let Some(rl) = &r.l {
+            Self::ordered(key, rl, comparator)?
+        } else {
+            Err(BoundsError::CannotJoin(key.clone()))?
+        }
+        Self::new(l.l, r.r, comparator)
+    }
+
+    pub fn equal_bound(l: &Option<A>, r: &Option<A>, comparator: &impl Comparator<A>) -> bool {
+        match (l, r) {
+            (None, None) => true,
+            (Some(kl), Some(kr)) => matches!(comparator.pick_smaller(kl, kr), Comparison::E),
+            _ => false,
+        }
+    }
+
+    pub fn equal(bl: &Self, br: &Self, comparator: &impl Comparator<A>) -> bool {
+        Self::equal_bound(&bl.l, &br.l, comparator) && Self::equal_bound(&bl.r, &br.r, comparator)
+    }
+}
diff --git a/src/rstd/collections/avl/bounds.rs b/src/rstd/collections/avl/bounds.rs
index 1376f04..341b11c 100644
--- a/src/rstd/collections/avl/bounds.rs
+++ b/src/rstd/collections/avl/bounds.rs
@@ -1,19 +1,8 @@
-use crate::flow::comparator::*;
+use crate::flow::{binary::bounds::*, comparator::*};
 use crate::func::context::*;
 
 use super::{binary::*, *};
 
-#[derive(Clone)]
-struct Bounds<A> {
-    l: Option<A>,
-    r: Option<A>,
-}
-
-pub enum BoundsError<A> {
-    BoundsViolated { l: A, r: A },
-    CannotJoin(A),
-}
-
 pub enum BoundError<A, E> {
     Avl(AvlError<E>),
     Bounds(BoundsError<A>),
@@ -56,76 +45,6 @@ pub struct BoundReference<'a, Ctx: Context<'a>, A: Mentionable<'a, Ctx>> {
     bounds: Bounds<A>,
 }
 
-impl<A: Clone> Bounds<A> {
-    fn unbound() -> Self {
-        Bounds { l: None, r: None }
-    }
-
-    fn ordered(l: &A, r: &A, comparator: &impl Comparator<A>) -> Result<(), BoundsError<A>> {
-        if let Comparison::R = comparator.pick_smaller(l, r) {
-            Err(BoundsError::BoundsViolated {
-                l: l.clone(),
-                r: r.clone(),
-            })
-        } else {
-            Ok(())
-        }
-    }
-
-    fn new(
-        l: Option<A>,
-        r: Option<A>,
-        comparator: &impl Comparator<A>,
-    ) -> Result<Self, BoundsError<A>> {
-        if let (Some(kl), Some(kr)) = (&l, &r) {
-            Self::ordered(kl, kr, comparator)?
-        }
-        Ok(Bounds { l, r })
-    }
-
-    fn split(
-        self,
-        key: &A,
-        comparator: &impl Comparator<A>,
-    ) -> Result<(Self, Self), BoundsError<A>> {
-        Ok((
-            Self::new(self.l, Some(key.clone()), comparator)?,
-            Self::new(Some(key.clone()), self.r, comparator)?,
-        ))
-    }
-
-    fn join(
-        l: Self,
-        r: Self,
-        key: &A,
-        comparator: &impl Comparator<A>,
-    ) -> Result<Self, BoundsError<A>> {
-        if let Some(lr) = &l.r {
-            Self::ordered(lr, key, comparator)?
-        } else {
-            Err(BoundsError::CannotJoin(key.clone()))?
-        }
-        if let Some(rl) = &r.l {
-            Self::ordered(key, rl, comparator)?
-        } else {
-            Err(BoundsError::CannotJoin(key.clone()))?
-        }
-        Self::new(l.l, r.r, comparator)
-    }
-
-    pub fn equal_bound(l: &Option<A>, r: &Option<A>, comparator: &impl Comparator<A>) -> bool {
-        match (l, r) {
-            (None, None) => true,
-            (Some(kl), Some(kr)) => matches!(comparator.pick_smaller(kl, kr), Comparison::E),
-            _ => false,
-        }
-    }
-
-    pub fn equal(bl: &Self, br: &Self, comparator: &impl Comparator<A>) -> bool {
-        Self::equal_bound(&bl.l, &br.l, comparator) && Self::equal_bound(&bl.r, &br.r, comparator)
-    }
-}
-
 pub type BoundSplit<'a, Ctx, A> = (BoundTree<'a, Ctx, A>, BoundTree<'a, Ctx, A>, A);
 
 impl<'a, Ctx: Context<'a>, A: Mentionable<'a, Ctx> + Clone> BoundNode<'a, Ctx, A> {