--- a/Dictionary.st	Thu Dec 31 06:46:33 2015 +0100
+++ b/Dictionary.st	Wed Jan 06 07:08:01 2016 +0100
@@ -247,7 +247,6 @@
     ^ true
 ! !
 
-
 !Dictionary methodsFor:'accessing'!
 
 associationAt:aKey
@@ -512,6 +511,18 @@
     "
 !
 
+decrementAt:aKey 
+    self incrementAt:aKey by:-1
+!
+
+incrementAt:aKey 
+    self incrementAt:aKey by:1
+!
+
+incrementAt:aKey by:count
+    self at:aKey put:(self at:aKey ifAbsent:[0])+count.
+!
+
 keyAtEqualValue:aValue
     "return the key whose value is equal (i.e. using #= for compare)
      to the argument, nil if none found.
@@ -2261,7 +2272,6 @@
     ^ aVisitor visitDictionary:self with:aParameter
 ! !
 
-
 !Dictionary class methodsFor:'documentation'!
 
 version