haskell: Phase 11 — Data.Map combining (unionWith/intersectionWith/difference)

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

lib/haskell/map.sx

@@ -320,3 +320,52 @@
         (append
           (hk-map-elems (hk-map-left m))
           (cons (hk-map-val m) (hk-map-elems (hk-map-right m))))))))
+
+(define
+  hk-map-union-with
+  (fn
+    (f m1 m2)
+    (reduce
+      (fn
+        (acc p)
+        (let
+          ((k (first p)) (v (nth p 1)))
+          (let
+            ((look (hk-map-lookup k acc)))
+            (cond
+              ((= (first look) "Just")
+                (hk-map-insert k (f (nth look 1) v) acc))
+              (:else (hk-map-insert k v acc))))))
+      m1
+      (hk-map-to-asc-list m2))))
+
+(define
+  hk-map-intersection-with
+  (fn
+    (f m1 m2)
+    (reduce
+      (fn
+        (acc p)
+        (let
+          ((k (first p)) (v1 (nth p 1)))
+          (let
+            ((look (hk-map-lookup k m2)))
+            (cond
+              ((= (first look) "Just")
+                (hk-map-insert k (f v1 (nth look 1)) acc))
+              (:else acc)))))
+      hk-map-empty
+      (hk-map-to-asc-list m1))))
+
+(define
+  hk-map-difference
+  (fn
+    (m1 m2)
+    (reduce
+      (fn
+        (acc p)
+        (let
+          ((k (first p)) (v (nth p 1)))
+          (cond ((hk-map-member k m2) acc) (:else (hk-map-insert k v acc)))))
+      hk-map-empty
+      (hk-map-to-asc-list m1))))