A map that returns the value associated with the closest key.

When looking up a key, returns the value for the key in the map that is
closest to the query. For numeric keys, distance is |query - key|.

Tie-breaking: When two keys are equidistant, use :< to prefer the
smaller key, or :> to prefer the larger key.

A set that returns the closest element to a query.

When looking up a value, returns the element in the set that is closest
to the query. For numeric keys, distance is |query - element|.

Tie-breaking: When two elements are equidistant, use :< to prefer the
smaller element, or :> to prefer the larger element.

Protocol extensions for interoperability with standard Clojure collections.

Extends ordered-collections protocols to:
- PersistentHashSet
- PersistentTreeSet
- PersistentTreeMap

This allows protocol functions like union, intersection, nearest, etc.
to work with standard Clojure sorted collections.

Persistent sorted multiset (bag) backed by a weight-balanced tree.

Internally an ordered map from elements to counts (longs). The public
API expands each entry into repeated elements: an element with count 3
appears three times in seq, reduce, and nth.

Persistent priority queue backed by a weight-balanced tree.

Internally an ordered map from priorities to vectors of values. Duplicate
priorities are stable in insertion order. The public API exposes
[priority value] pairs; the vector grouping is hidden.

A map from non-overlapping ranges to values.

Unlike IntervalMap (which allows overlapping intervals), RangeMap enforces
that ranges never overlap. When inserting a new range, any overlapping
portions of existing ranges are removed.

SEMANTICS (compatible with Guava's TreeRangeMap):
- `assoc` (put): inserts range, carving out overlaps. Does NOT coalesce.
- `assoc-coalescing` (putCoalescing): inserts and coalesces adjacent
  same-value ranges.

RANGE SEMANTICS:
Ranges are half-open intervals [lo, hi) by default:
- [0 10] contains 0, 1, 2, ..., 9 but NOT 10

PERFORMANCE:
- Point lookup: O(log n)
- Insert/assoc: O(k log n) where k = number of overlapping ranges
- Coalescing insert: O(k log n)
- Remove: O(k log n)
For typical use (k=1-3 overlaps), effectively O(log n).

Persistent rope-like indexed sequence backed by an implicit-index
weight-balanced tree.

             ┌─────────────┐
             │ key: 3      │
             │ val: 40     │
             │ agg: 150 ◄──────── sum of entire tree
             └──────┬──────┘
        ┌───────────┴───────────┐
 ┌──────┴──────┐         ┌──────┴──────┐
 │ key: 1      │         │ key: 4      │
 │ val: 20     │         │ val: 50     │
 │ agg: 30 ◄───────      │ agg: 80 ◄───────
 └──────┬──────┘   │     └──────┬──────┘   │
        │          │            │          │
 ┌──────┴──────┐   │     ┌──────┴──────┐   │
 │ key: 0      │   │     │ key: 5      │   │
 │ val: 10     │   │     │ val: 30     │   │
 │ agg: 10     │   │     │ agg: 30     │   │
 └─────────────┘   │     └─────────────┘   │
                   │                       │
        10 + 20 = 30              50 + 30 = 80

A segment tree for efficient range aggregate queries.

Supports O(log n) point updates and O(log n) range queries for any
associative operation (sum, min, max, gcd, etc.).

CONCEPT:
Each node stores an aggregate of its entire subtree. For sum:

                 ┌─────────────┐
                 │ key: 3      │
                 │ val: 40     │
                 │ agg: 150 ◄──────── sum of entire tree
                 └──────┬──────┘
            ┌───────────┴───────────┐
     ┌──────┴──────┐         ┌──────┴──────┐
     │ key: 1      │         │ key: 4      │
     │ val: 20     │         │ val: 50     │
     │ agg: 30 ◄───────      │ agg: 80 ◄───────
     └──────┬──────┘   │     └──────┬──────┘   │
            │          │            │          │
     ┌──────┴──────┐   │     ┌──────┴──────┐   │
     │ key: 0      │   │     │ key: 5      │   │
     │ val: 10     │   │     │ val: 30     │   │
     │ agg: 10     │   │     │ agg: 30     │   │
     └─────────────┘   │     └─────────────┘   │
                       │                       │
            10 + 20 = 30              50 + 30 = 80

RANGE QUERY: query(1, 4) = sum of indices 1,2,3,4
Uses aggregates to avoid visiting every node - O(log n).

EXAMPLE:
  (def st (segment-tree + 0 {0 10, 1 20, 2 30, 3 40, 4 50}))
  (query st 0 4)     ; => 150 (sum of all)
  (query st 1 3)     ; => 90 (20 + 30 + 40)
  (update st 2 100)  ; => new tree with index 2 = 100
  (query st 1 3)     ; => 160 (20 + 100 + 40)