map-difference utility function.

marick · Mar 23, 2011 · 4451cf5 · 4451cf5
1 parent 3db0360
commit 4451cf5
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diff --git a/src/midje/util/form_utils.clj b/src/midje/util/form_utils.clj
@@ -1,7 +1,8 @@
 ;; -*- indent-tabs-mode: nil -*-
 
 (ns midje.util.form-utils
-  (:use [midje.util laziness]))
+  (:use [midje.util laziness]
+        [clojure.set :only [difference]]))
 
 (defn regex? [thing]
   (= (class thing) java.util.regex.Pattern))
@@ -71,3 +72,6 @@
          (map (fn [function arg] (apply function [arg]))
               functions arglist))
        arglists))
+
+(defn map-difference [bigger smaller]
+  (select-keys bigger (difference (set (keys bigger)) (set (keys smaller)))))
diff --git a/test/midje/util/t_form_utils.clj b/test/midje/util/t_form_utils.clj
@@ -49,3 +49,6 @@
   (hash-map-duplicates-ok :a 1 :b 2) => {:a 1 :b 2}
   (hash-map-duplicates-ok :a 1 :b 2 :b 33333) => {:a 1 :b 33333})
 
+
+(fact "map-difference"
+  (map-difference {:a 1, :b 2} {:a 1, :c 3}) => {:b 2})