From 54569ea2e5586e4b60341c3c9cbfd4a590c85ea4 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Dominik=20Pant=C5=AF=C4=8Dek?=
 <dominik.pantucek@trustica.cz>
Date: Thu, 6 Apr 2023 19:21:50 +0200
Subject: [PATCH] Functional dict-update.

---
 src/dictionary.scm | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/src/dictionary.scm b/src/dictionary.scm
index 966ba61..164776a 100644
--- a/src/dictionary.scm
+++ b/src/dictionary.scm
@@ -37,6 +37,7 @@
   dict-map
   dict-filter
   dict-reduce
+  dict-update
   dictionary-tests!
   )
 
@@ -145,6 +146,11 @@
 	 (loop (cdr d)
 	       (proc acc (caar d) (cdar d))))))
 
+ ;; Functional update
+ (define (dict-update d k proc . dfls)
+   (dict-set d k
+	     (proc (apply dict-ref d k dfls))))
+
  ;; Performs self-tests of the dictionary module.
  (define (dictionary-tests!)
    (run-tests