Add kvplist-merge function, test and readme text

3 files changed, 23 insertions, 3 deletions

diff --git a/README.creole b/README.creole
index b4a58ae..d5e49ab 100644
--- a/README.creole
+++ b/README.creole
@@ -145,9 +145,10 @@ Filter the plist to just those matching //keys//.
 
 [[kvalist->filter-keys]] is actually used to do this work.
 
+=== kvplist->merge old-plist new-plist ===
+
+Merge the keys from new-plist into old-plist and return the new plist.
 
 === kvplist2->filter-keys plist2 &rest keys ===
 
 Return the //plist2// (a list of plists) filtered to the //keys//.
-
-
diff --git a/kv-tests.el b/kv-tests.el
index 4a4823f..7cc6eed 100644
--- a/kv-tests.el
+++ b/kv-tests.el
@@ -179,4 +179,11 @@
      (list :key1 "value1" :key2 t :key3 '(big list of symbols) :key4 10)
      'key1 'key4))))
 
+(ert-deftest kvplist-merge ()
+  (should
+   (equal
+    '(:key1 "value1" :key2 "new value" :key3 "entirely new")
+    (kvplist-merge '(:key1 "value1" :key2 "old value")
+                   '(:key2 "new value" :key3 "entirely new")))))
+
 ;;; kv-tests.el ends here
diff --git a/kv.el b/kv.el
index ffed5b6..57958e1 100644
--- a/kv.el
+++ b/kv.el
@@ -179,7 +179,7 @@ The keys are expected to be :prefixed and the colons are removed.
 The keys in the resulting alist are symbols."
   (when plist
     (loop for (key value . rest) on plist by 'cddr
-	  collect (cons (keyword->symbol key) value))))
+    collect (cons (keyword->symbol key) value))))
 
 (defun kvalist2->plist (alist2)
   "Convert a list of alists too a list of plists."
@@ -385,6 +385,18 @@ SEXP will describe the structure desired."
 
 (defalias 'map-bind 'kvmap-bind)
 
+(defun kvplist-merge (old new)
+  "Merges two plists. The keys from NEW will overwrite the ones in OLD."
+  (let ((key (car new))
+        (val (cadr new))
+        (new (cddr new)))
+    (while (and key val)
+      (setq old (plist-put old key val))
+      (setq key (car new))
+      (setq val (cadr new))
+      (setq new (cddr new)))
+    old))
+
 (provide 'kv)
 (provide 'dotassoc)