--- a/Collection.st	Fri Jan 20 19:55:46 2017 +0100
+++ b/Collection.st	Fri Jan 20 19:59:28 2017 +0100
@@ -343,7 +343,6 @@
     ^ self
 ! !
 
-
 !Collection methodsFor:'Compatibility-ANSI'!
 
 identityIncludes:anObject
@@ -426,11 +425,13 @@
 difference: aCollection
     "Answer the set-theoretic difference of two collections."
 
-    ^ self reject:[:each | aCollection includes: each]
+    ^ self \ aCollection
 
     "
      #(0 2 4 6 8) difference:#(2 4)   
     "
+
+    "Modified: / 20-01-2017 / 19:21:35 / stefan"
 !
 
 gather:aBlock
@@ -3553,7 +3554,7 @@
 
     |newCollection|
 
-    newCollection := self species new.
+    newCollection := self speciesForAdding new.
     self do:[:each |
         (aBlock value:each) ifTrue:[newCollection add:each].
     ].
@@ -3565,6 +3566,7 @@
     "
 
     "Modified: / 07-08-2010 / 16:26:40 / cg"
+    "Modified: / 20-01-2017 / 17:42:33 / stefan"
 !
 
 select:aBlock as:aCollectionClass
@@ -5281,43 +5283,36 @@
      which are NOT also contained in the aCollection
      For large collections you better use a Set for aCollection"
 
-
-    |newCollection|
-
-    newCollection := self speciesForAdding new.
-    self do:[:element |
-        (aCollection includes:element) ifFalse:[
-            newCollection add:element
-        ]
-    ].
-    ^ newCollection
+    ^ self select:[:eachElement | (aCollection includes:eachElement) not].
 
     "
      #(0 1 2 3 4 5 6 7 8 9) \ #(1 2 3) asSet
      #(0 1 2 3 4 5 6 7 8 9) \ #(1 2 3)
-    ('hello' \ 'l') asString
-    "
+     ('hello' \ 'l')
+
+     (Dictionary withKeysAndValues:#(1 'uno' 2 'due' 3 'tre' 4 'quatro'))
+        \ (Dictionary withKeysAndValues:#(1 'uno'  4 'quatro'))
+    "
+
+    "Modified (comment): / 20-01-2017 / 19:28:00 / stefan"
 !
 
 intersect:aCollection
     "return a new set containing all elements of the receiver,
      which are also contained in the argument collection.
-     For large collections you better use a Set for self"
-
-    |newCollection|
-
-    newCollection := self speciesForAdding new.
-    aCollection do:[:element |
-        (self includes:element) ifTrue:[
-            newCollection add:element
-        ]
-    ].
-    ^ newCollection
+     For large collections you better use a Set for aCollection"
+
+    ^ aCollection select:[:eachElement | self includes:eachElement].
 
     "
      #(0 1 2 3 4 5 6 7 8 9) asSet intersect:#(1 2 3 11)
      #(0 1 2 3 4 5 6 7 8 9) intersect:#(1 2 3 11)
-    "
+
+     (Dictionary withKeysAndValues:#(1 'uno' 2 'due' 3 'tre' 4 'quatro'))
+        intersect:(Dictionary withKeysAndValues:#(1 'uno'  4 'quatro' 5 'cinque'))
+    "
+
+    "Modified: / 20-01-2017 / 19:33:14 / stefan"
 !
 
 union:aCollection
@@ -5334,7 +5329,12 @@
     "
      #(0 2 4 6 8) union:#(1 3 5 7)
      #(0 2 4 6 8) union:#(0 1 3 5 7)
-    "
+
+     (Dictionary withKeysAndValues:#(1 'uno' 2 'due' 3 'tre' 4 'quatro'))
+        union:(Dictionary withKeysAndValues:#(1 'uno'  4 'quatro' 5 'cinque'))
+    "
+
+    "Modified (comment): / 20-01-2017 / 19:35:23 / stefan"
 !
 
 xor:aCollection
@@ -5361,6 +5361,9 @@
 
     "
      #(0 1 2 3 4 5 6 7 8 9) xor:#(1 2 3 11)
+     (Dictionary withKeysAndValues:#(1 'uno' 2 'due' 3 'tre' 4 'quatro'))
+        xor:(Dictionary withKeysAndValues:#(1 'uno'  4 'quatro' 5 'cinque'))
+
     "
 
     "
@@ -5371,6 +5374,8 @@
      c1 symmetricDifference:c2.
      self assert:(c1 symmetricDifference:c2) asSet = (c2 symmetricDifference:c1) asSet
     "
+
+    "Modified (comment): / 20-01-2017 / 19:37:58 / stefan"
 ! !
 
 !Collection methodsFor:'sorting & reordering'!