Add assoc-in for nested structures

Author: jbouwman

src/algorithm/hamt.lisp

@@ -17,6 +17,7 @@
   (:export #:+empty+
            #:immutable-map
            #:assoc
+           #:assoc-in
            #:contains-p
            #:difference
            #:dissoc
@@ -422,6 +423,16 @@ Returns (values new-node inserted-p) where inserted-p is true for new insertions
       (make-immutable-map new-root (+ (immutable-map-count map)
                                       (if inserted 1 0))))))
 
+(defun assoc-in (map keys value)
+  "Associate VALUE in a nested MAP structure, where KEYS is a sequence of keys."
+  (if (null keys)
+      value
+      (let ((k (car keys)))
+        (assoc map k
+               (assoc-in (get map k +empty+)
+                         (cdr keys)
+                         value)))))
+
 (defun reduce (function map &optional (initial-value +empty+))
   "Reduce over key-value pairs in the map"
   (cl:reduce (lambda (acc pair)