haskell: Phase 11 — Data.Map updating (adjust/insertWith/insertWithKey/alter)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

plans/haskell-completeness.md

@@ -187,7 +187,7 @@ No OCaml changes are needed. The view type is fully representable as an SX dict.
 - [x] Bulk operations: `fromList`, `toList`, `toAscList`, `keys`, `elems`.
 - [x] Combining: `unionWith`, `intersectionWith`, `difference`.
 - [x] Transforming: `foldlWithKey`, `foldrWithKey`, `mapWithKey`, `filterWithKey`.
-- [ ] Updating: `adjust`, `insertWith`, `insertWithKey`, `alter`.
+- [x] Updating: `adjust`, `insertWith`, `insertWithKey`, `alter`.
 - [ ] Module wiring: `import Data.Map` and `import qualified Data.Map as Map`
   resolve to the `map.sx` namespace dict in the eval import handler.
 - [ ] Unit tests in `lib/haskell/tests/map.sx` (≥ 20 tests: empty, singleton,
@@ -304,6 +304,12 @@ No OCaml changes are needed. The view type is fully representable as an SX dict.
 
 _Newest first._
 
+**2026-05-07** — Phase 11 updating (adjust/insertWith/insertWithKey/alter):
+- `adjust` recurses to find the key, replaces value with `f(v)`; no-op when
+  missing. `insertWith` and `insertWithKey` recurse with rebalance and use
+  `f new old` (or `f k new old`) when the key exists. `alter` is the most
+  general, implemented as `lookup → f → either delete or insert`.
+
 **2026-05-07** — Phase 11 transforming (foldlWithKey/foldrWithKey/mapWithKey/filterWithKey):
 - Folds traverse in-order. `foldlWithKey f acc m` walks left → key/val → right
   threading the accumulator, so left-folding `(\acc k v -> acc ++ k ++ v)` over