Maps - add merge-with and map entries as seq

resources/koans.clj

@@ -80,8 +80,10 @@
                 "February"
                 1 "January"
                 :c 3 
+                2
                 2010 2014 2018
-                "PyeongChang" "Sochi" "Vancouver"]}]
+                "PyeongChang" "Sochi" "Vancouver"
+                2 3]}]
 
  ["07_functions" {"__" [81
                      20

src/koans/06_maps.clj

@@ -44,6 +44,9 @@
   "Create a new map by merging" 
   (= {:a 1 :b 2 __ __} (merge {:a 1 :b 2} {:c 3}))
 
+  "Specify how to handle entries with same keys when merging"
+  (= {:a 1 :b __ :c 3} (merge-with + {:a 1 :b 1} {:b 1 :c 3}))
+  
   "Often you will need to get the keys, but the order is undependable"
   (= (list __ __ __)
      (sort (keys { 2014 "Sochi" 2018 "PyeongChang" 2010 "Vancouver"})))
@@ -51,3 +54,10 @@
   "You can get the values in a similar way"
   (= (list __ __ __)
      (sort (vals {2010 "Vancouver" 2014 "Sochi" 2018 "PyeongChang"}))))
+
+  "You can even iterate over the map entries as a seq"
+  (= {:a __ :b __}
+     (into {}
+           (map
+            (fn[[k v]] [k (inc v)])
+            {:a 1 :b 2})))