diff -r 1f19c6bbf07b -r 3868555d135c src/bisection_tree/aggregator.rs
--- a/src/bisection_tree/aggregator.rs	Sun Apr 27 20:29:43 2025 -0500
+++ b/src/bisection_tree/aggregator.rs	Fri May 15 14:46:30 2026 -0500
@@ -2,9 +2,8 @@
 Aggregation / summarisation of information in branches of bisection trees.
 */
 
+pub use crate::bounds::Bounds;
 use crate::types::*;
-use crate::sets::Set;
-use crate::instance::Instance;
 
 /// Trait for aggregating information about a branch of a [bisection tree][super::BT].
 ///
@@ -19,180 +18,60 @@
 ///    of a function on a greater domain from bounds on subdomains
 ///    (in practise [`Cube`][crate::sets::Cube]s).
 ///
-pub trait Aggregator : Clone + Sync + Send + 'static + std::fmt::Debug {
+pub trait Aggregator: Clone + Sync + Send + 'static + std::fmt::Debug {
     /// Aggregate a new data to current state.
-    fn aggregate<I>(&mut self, aggregates : I)
-    where I : Iterator<Item=Self>;
+    fn aggregate<I>(&mut self, aggregates: I)
+    where
+        I: Iterator<Item = Self>;
 
     /// Summarise several other aggregators, resetting current state.
-    fn summarise<'a, I>(&'a mut self, aggregates : I)
-    where I : Iterator<Item=&'a Self>;
+    fn summarise<'a, I>(&'a mut self, aggregates: I)
+    where
+        I: Iterator<Item = &'a Self>;
 
     /// Create a new “empty” aggregate data.
     fn new() -> Self;
 }
 
 /// An [`Aggregator`] that doesn't aggregate anything.
-#[derive(Clone,Debug)]
+#[derive(Clone, Debug)]
 pub struct NullAggregator;
 
 impl Aggregator for NullAggregator {
-    fn aggregate<I>(&mut self, _aggregates : I)
-    where I : Iterator<Item=Self> {}
-
-    fn summarise<'a, I>(&'a mut self, _aggregates : I)
-    where I : Iterator<Item=&'a Self> {}
-
-    fn new() -> Self { NullAggregator }
-}
-
-/// Upper and lower bounds on an `F`-valued function.
-#[derive(Copy,Clone,Debug)]
-pub struct Bounds<F>(
-    /// Lower bound
-    pub F,
-    /// Upper bound
-    pub F
-);
-
-impl<F : Copy> Bounds<F> {
-    /// Returns the lower bound
-    #[inline]
-    pub fn lower(&self) -> F { self.0 }
-
-    /// Returns the upper bound
-    #[inline]
-    pub fn upper(&self) -> F { self.1 }
-}
-
-impl<F : Float> Bounds<F> {
-    /// Returns a uniform bound.
-    ///
-    /// This is maximum over the absolute values of the upper and lower bound.
-    #[inline]
-    pub fn uniform(&self) -> F {
-        let &Bounds(lower, upper) = self;
-        lower.abs().max(upper.abs())
+    fn aggregate<I>(&mut self, _aggregates: I)
+    where
+        I: Iterator<Item = Self>,
+    {
     }
 
-    /// Construct a bounds, making sure `lower` bound is less than `upper`
-    #[inline]
-    pub fn corrected(lower : F, upper : F) -> Self {
-        if lower <= upper {
-            Bounds(lower, upper)
-        } else {
-            Bounds(upper, lower)
-        }
+    fn summarise<'a, I>(&'a mut self, _aggregates: I)
+    where
+        I: Iterator<Item = &'a Self>,
+    {
     }
 
-    /// Refine the lower bound
-    #[inline]
-    pub fn refine_lower(&self, lower : F) -> Self {
-        let &Bounds(l, u) = self;
-        debug_assert!(l <= u);
-        Bounds(l.max(lower), u.max(lower))
-    }
-
-    /// Refine the lower bound
-    #[inline]
-    pub fn refine_upper(&self, upper : F) -> Self {
-        let &Bounds(l, u) = self;
-        debug_assert!(l <= u);
-        Bounds(l.min(upper), u.min(upper))
+    fn new() -> Self {
+        NullAggregator
     }
 }
 
-impl<'a, F : Float> std::ops::Add<Self> for Bounds<F> {
-    type Output = Self;
-    #[inline]
-    fn add(self, Bounds(l2, u2) : Self) -> Self::Output {
-        let Bounds(l1, u1) = self;
-        debug_assert!(l1 <= u1 && l2 <= u2);
-        Bounds(l1 + l2, u1 + u2)
-    }
-}
-
-impl<'a, F : Float> std::ops::Mul<Self> for Bounds<F> {
-    type Output = Self;
-    #[inline]
-    fn mul(self, Bounds(l2, u2) : Self) -> Self::Output {
-        let Bounds(l1, u1) = self;
-        debug_assert!(l1 <= u1 && l2 <= u2);
-        let a = l1 * l2;
-        let b = u1 * u2;
-        // The order may flip when negative numbers are involved, so need min/max
-        Bounds(a.min(b), a.max(b))
-    }
-}
-
-impl<F : Float> std::iter::Product for Bounds<F> {
+impl<F: Float> Aggregator for Bounds<F> {
     #[inline]
-    fn product<I>(mut iter: I) -> Self
-    where I: Iterator<Item = Self> {
-        match iter.next() {
-            None => Bounds(F::ZERO, F::ZERO),
-            Some(init) => iter.fold(init, |a, b| a*b)
-        }
-    }
-}
-
-impl<F : Float> Set<F> for Bounds<F> {
-    fn contains<I : Instance<F>>(&self, item : I) -> bool {
-        let v = item.own();
-        let &Bounds(l, u) = self;
-        debug_assert!(l <= u);
-        l <= v && v <= u
-    }
-}
-
-impl<F : Float> Bounds<F> {
-    /// Calculate a common bound (glb, lub) for two bounds.
-    #[inline]
-    pub fn common(&self, &Bounds(l2, u2) : &Self) -> Self {
-        let &Bounds(l1, u1) = self;
-        debug_assert!(l1 <= u1 && l2 <= u2);
-        Bounds(l1.min(l2), u1.max(u2))
-    }
-
-    /// Indicates whether `Self` is a superset of the argument bound.
-    #[inline]
-    pub fn superset(&self, &Bounds(l2, u2) : &Self) -> bool {
-        let &Bounds(l1, u1) = self;
-        debug_assert!(l1 <= u1 && l2 <= u2);
-        l1 <= l2 && u2 <= u1
-    }
-
-    /// Returns the greatest bound contained by both argument bounds, if one exists.
-    #[inline]
-    pub fn glb(&self, &Bounds(l2, u2) : &Self) -> Option<Self> {
-        let &Bounds(l1, u1) = self;
-        debug_assert!(l1 <= u1 && l2 <= u2);
-        let l = l1.max(l2);
-        let u = u1.min(u2);
-        debug_assert!(l <= u);
-        if l < u {
-            Some(Bounds(l, u))
-        } else {
-            None
-        }
-    }
-}
-
-impl<F : Float> Aggregator for Bounds<F> {
-    #[inline]
-    fn aggregate<I>(&mut self, aggregates : I)
-    where I : Iterator<Item=Self> {
+    fn aggregate<I>(&mut self, aggregates: I)
+    where
+        I: Iterator<Item = Self>,
+    {
         *self = aggregates.fold(*self, |a, b| a + b);
     }
 
     #[inline]
-    fn summarise<'a, I>(&'a mut self, mut aggregates : I)
-    where I : Iterator<Item=&'a Self> {
+    fn summarise<'a, I>(&'a mut self, mut aggregates: I)
+    where
+        I: Iterator<Item = &'a Self>,
+    {
         *self = match aggregates.next() {
             None => Bounds(F::ZERO, F::ZERO), // No parts in this cube; the function is zero
-            Some(&bounds) => {
-                aggregates.fold(bounds, |a, b| a.common(b))
-            }
+            Some(&bounds) => aggregates.fold(bounds, |a, b| a.common(b)),
         }
     }