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diff --git a/src/soft.rs b/src/soft.rs
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+//! [Soft deletion](https://en.wiktionary.org/wiki/soft_deletion) for nearest neighbor search.
+
+use super::forest::{KdForest, VpForest};
+
+use acap::distance::Proximity;
+use acap::kd::FlatKdTree;
+use acap::vp::FlatVpTree;
+use acap::{NearestNeighbors, Neighborhood};
+
+use std::iter;
+use std::iter::FromIterator;
+use std::mem;
+
+/// A trait for objects that can be soft-deleted.
+pub trait SoftDelete {
+    /// Check whether this item is deleted.
+    fn is_deleted(&self) -> bool;
+}
+
+/// Blanket [SoftDelete] implementation for references.
+impl<'a, T: SoftDelete> SoftDelete for &'a T {
+    fn is_deleted(&self) -> bool {
+        (*self).is_deleted()
+    }
+}
+
+/// [Neighborhood] wrapper that ignores soft-deleted items.
+#[derive(Debug)]
+struct SoftNeighborhood<N>(N);
+
+impl<K, V, N> Neighborhood<K, V> for SoftNeighborhood<N>
+where
+    V: SoftDelete,
+    K: Proximity<V>,
+    N: Neighborhood<K, V>,
+{
+    fn target(&self) -> K {
+        self.0.target()
+    }
+
+    fn contains<D>(&self, distance: D) -> bool
+    where
+        D: PartialOrd<K::Distance>
+    {
+        self.0.contains(distance)
+    }
+
+    fn consider(&mut self, item: V) -> K::Distance {
+        if item.is_deleted() {
+            self.target().distance(&item)
+        } else {
+            self.0.consider(item)
+        }
+    }
+}
+
+/// A [NearestNeighbors] implementation that supports [soft deletes](https://en.wiktionary.org/wiki/soft_deletion).
+#[derive(Debug)]
+pub struct SoftSearch<T>(T);
+
+impl<T, U> SoftSearch<U>
+where
+    T: SoftDelete,
+    U: FromIterator<T> + IntoIterator<Item = T>,
+{
+    /// Create a new empty soft index.
+    pub fn new() -> Self {
+        Self(iter::empty().collect())
+    }
+
+    /// Push a new item into this index.
+    pub fn push(&mut self, item: T)
+    where
+        U: Extend<T>,
+    {
+        self.0.extend(iter::once(item));
+    }
+
+    /// Rebuild this index, discarding deleted items.
+    pub fn rebuild(&mut self) {
+        let items = mem::replace(&mut self.0, iter::empty().collect());
+        self.0 = items.into_iter().filter(|e| !e.is_deleted()).collect();
+    }
+}
+
+impl<T, U> Default for SoftSearch<U>
+where
+    T: SoftDelete,
+    U: FromIterator<T> + IntoIterator<Item = T>,
+{
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+impl<T, U: Extend<T>> Extend<T> for SoftSearch<U> {
+    fn extend<I: IntoIterator<Item = T>>(&mut self, iter: I) {
+        self.0.extend(iter);
+    }
+}
+
+impl<T, U: FromIterator<T>> FromIterator<T> for SoftSearch<U> {
+    fn from_iter<I: IntoIterator<Item = T>>(iter: I) -> Self {
+        Self(U::from_iter(iter))
+    }
+}
+
+impl<T: IntoIterator> IntoIterator for SoftSearch<T> {
+    type Item = T::Item;
+    type IntoIter = T::IntoIter;
+
+    fn into_iter(self) -> Self::IntoIter {
+        self.0.into_iter()
+    }
+}
+
+impl<K, V, T> NearestNeighbors<K, V> for SoftSearch<T>
+where
+    K: Proximity<V>,
+    V: SoftDelete,
+    T: NearestNeighbors<K, V>,
+{
+    fn search<'k, 'v, N>(&'v self, neighborhood: N) -> N
+    where
+        K: 'k,
+        V: 'v,
+        N: Neighborhood<&'k K, &'v V>
+    {
+        self.0.search(SoftNeighborhood(neighborhood)).0
+    }
+}
+
+/// A k-d forest that supports soft deletes.
+pub type SoftKdForest<T> = SoftSearch<KdForest<T>>;
+
+/// A k-d tree that supports soft deletes.
+pub type SoftKdTree<T> = SoftSearch<FlatKdTree<T>>;
+
+/// A VP forest that supports soft deletes.
+pub type SoftVpForest<T> = SoftSearch<VpForest<T>>;
+
+/// A VP tree that supports soft deletes.
+pub type SoftVpTree<T> = SoftSearch<FlatVpTree<T>>;
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    use acap::coords::Coordinates;
+    use acap::euclid::{euclidean_distance, Euclidean, EuclideanDistance};
+    use acap::Neighbor;
+
+    type Point = Euclidean<[f32; 3]>;
+
+    #[derive(Debug, PartialEq)]
+    struct SoftPoint {
+        point: [f32; 3],
+        deleted: bool,
+    }
+
+    impl SoftPoint {
+        fn new(x: f32, y: f32, z: f32) -> Self {
+            Self {
+                point: [x, y, z],
+                deleted: false,
+            }
+        }
+
+        fn deleted(x: f32, y: f32, z: f32) -> Self {
+            Self {
+                point: [x, y, z],
+                deleted: true,
+            }
+        }
+    }
+
+    impl SoftDelete for SoftPoint {
+        fn is_deleted(&self) -> bool {
+            self.deleted
+        }
+    }
+
+    impl Proximity for SoftPoint {
+        type Distance = EuclideanDistance<f32>;
+
+        fn distance(&self, other: &Self) -> Self::Distance {
+            euclidean_distance(&self.point, &other.point)
+        }
+    }
+
+    impl Coordinates for SoftPoint {
+        type Value = <Point as Coordinates>::Value;
+
+        fn dims(&self) -> usize {
+            self.point.dims()
+        }
+
+        fn coord(&self, i: usize) -> Self::Value {
+            self.point.coord(i)
+        }
+    }
+
+    impl Proximity<SoftPoint> for Point {
+        type Distance = EuclideanDistance<f32>;
+
+        fn distance(&self, other: &SoftPoint) -> Self::Distance {
+            euclidean_distance(&self, &other.point)
+        }
+    }
+
+    fn test_index<T>(index: &T)
+    where
+        T: NearestNeighbors<Point, SoftPoint>,
+    {
+        let target = Euclidean([0.0, 0.0, 0.0]);
+
+        assert_eq!(
+            index.nearest(&target).expect("No nearest neighbor found"),
+            Neighbor::new(&SoftPoint::new(1.0, 2.0, 2.0), 3.0)
+        );
+
+        assert_eq!(index.nearest_within(&target, 2.0), None);
+        assert_eq!(
+            index.nearest_within(&target, 4.0).expect("No nearest neighbor found within 4.0"),
+            Neighbor::new(&SoftPoint::new(1.0, 2.0, 2.0), 3.0)
+        );
+
+        assert_eq!(
+            index.k_nearest(&target, 3),
+            vec![
+                Neighbor::new(&SoftPoint::new(1.0, 2.0, 2.0), 3.0),
+                Neighbor::new(&SoftPoint::new(3.0, 4.0, 0.0), 5.0),
+                Neighbor::new(&SoftPoint::new(2.0, 3.0, 6.0), 7.0),
+            ]
+        );
+
+        assert_eq!(
+            index.k_nearest_within(&target, 3, 6.0),
+            vec![
+                Neighbor::new(&SoftPoint::new(1.0, 2.0, 2.0), 3.0),
+                Neighbor::new(&SoftPoint::new(3.0, 4.0, 0.0), 5.0),
+            ]
+        );
+        assert_eq!(
+            index.k_nearest_within(&target, 3, 8.0),
+            vec![
+                Neighbor::new(&SoftPoint::new(1.0, 2.0, 2.0), 3.0),
+                Neighbor::new(&SoftPoint::new(3.0, 4.0, 0.0), 5.0),
+                Neighbor::new(&SoftPoint::new(2.0, 3.0, 6.0), 7.0),
+            ]
+        );
+    }
+
+    fn test_soft_index<T>(index: &mut SoftSearch<T>)
+    where
+        T: Extend<SoftPoint>,
+        T: FromIterator<SoftPoint>,
+        T: IntoIterator<Item = SoftPoint>,
+        T: NearestNeighbors<Point, SoftPoint>,
+    {
+        let points = vec![
+            SoftPoint::deleted(0.0, 0.0, 0.0),
+            SoftPoint::new(3.0, 4.0, 0.0),
+            SoftPoint::new(5.0, 0.0, 12.0),
+            SoftPoint::new(0.0, 8.0, 15.0),
+            SoftPoint::new(1.0, 2.0, 2.0),
+            SoftPoint::new(2.0, 3.0, 6.0),
+            SoftPoint::new(4.0, 4.0, 7.0),
+        ];
+
+        for point in points {
+            index.push(point);
+        }
+        test_index(index);
+
+        index.rebuild();
+        test_index(index);
+    }
+
+    #[test]
+    fn test_soft_kd_forest() {
+        test_soft_index(&mut SoftKdForest::new());
+    }
+
+    #[test]
+    fn test_soft_vp_forest() {
+        test_soft_index(&mut SoftVpForest::new());
+    }
+}