feat: Progress towards comfortable Lisp editing

users/crumb/programs/emacs/lib/syd-prelude.el

@@ -66,4 +66,12 @@
               (put ',hook-name 'permanent-local-hook t)
               (add-hook ,hook-or-function* #',hook-name))))))
 
+(defun syd-plist-put (plist prop new-val)
+  "Immutably update a single property of PLIST.  Like `plist-put', but PLIST is
+not mutated; a new plist is returned."
+  (cl-loop for (prop* old-val) on plist by #'cddr
+           appending (if (eq prop prop*)
+                         (list prop* new-val)
+                       (list prop* old-val))))
+
 (provide 'syd-prelude)