Lookup (incr_map.Incr_map.Make.Lookup)

('k, 'v) Lookup.t provides a way to lookup keys in a map which uses symmetric diffs to trigger updates of the lookups.

The complexity of an update depends on:

n: the number of keys in the larger of the old/updated input map
k: the number of lookup nodes created using find
m: the number of elements in the symdiff of the maps
symdiff(n): the cost of performing the symdiff on the map (m <= symdiff(n) <= n)

Each update should cost O(symdiff(n) + m * log k), so this will be efficient when there are a lot of lookups (close to n) into a map which can be efficiently symdiffed (and therefore has a small number of changes also). The cost of updating when performing the same lookups by means of Incr.map ~f:(fun m -> Map.find m key) is O(k * log n).

val create : ?⁠data_equal:('v ‑> 'v ‑> bool) ‑> ('k, 'v, 'cmp) Core_kernel.Map.t Incr.t ‑> comparator:('k, 'cmp) Core_kernel.Comparator.t ‑> ('k, 'v, 'cmp) t

Create the lookup structure on an incremental map.

val find : ('k, 'v, _) t ‑> 'k ‑> 'v option Incr.t

Create a node which performs Map.find on the input map.

find (create incr_map) key should be equivalent to Incr.map ~f:(fun m -> Map.find m key) incr_map, but when you call find many times for a single create the nodes should update more efficiently in stabilisation when incr_map changes in a way which can be efficiently diffed.

This will re-use existing nodes when it can, but will not always do so.