--- a/Collection.st	Thu Aug 19 21:39:34 2010 +0100
+++ b/Collection.st	Thu Aug 26 11:12:57 2010 +0100
@@ -458,6 +458,39 @@
     self emptyCollectionError.
 !
 
+at:aKey ifNilOrAbsentPut:valueBlock
+    "try to fetch the element at aKey. If either the key is invalid (as in a Dictionary)
+     or there is no element stored under that key (as in an Array), set the element 
+     from the valueBlock and return it.
+     Useful for lazy initialization of collections."
+
+    |val|
+
+    val := self at:aKey ifAbsent:[ self at:aKey put:valueBlock value ].
+    val isNil ifTrue:[
+        self at:aKey put:(val := valueBlock value).
+    ].
+    ^ val
+
+    "
+     |d|
+
+     d := Dictionary new.
+     d at:#foo ifNilOrAbsentPut:[ 'hello' ]. 
+     d     
+    "
+
+    "
+     |a|
+
+     a := Array new:10.
+     a at:1 ifNilOrAbsentPut:[ 'hello' ].  
+     a    
+    "
+
+    "Created: / 24-08-2010 / 17:07:21 / cg"
+!
+
 atAll:indexCollection put:anObject
     "put anObject into all indexes from indexCollection in the receiver.
      This abstract implementation requires that the receiver supports
@@ -1233,8 +1266,8 @@
 !
 
 sum:aBlock
-    "for each element in the receiver, evaluate the argument, aBlock
-     and sum up the results. Return the total sum or 0 for an empty collection.
+    "for each element in the receiver, evaluate the argument, aBlock and sum up the results. 
+     Return the total sum or 0 for an empty collection.
      Similar to (self collect...) sum, but avoids creation of an intermediate collection."
 
     |sum|
@@ -1255,6 +1288,8 @@
      ((1 to:10) collect:[:n | n squared]) sum 
      ((1 to:10) sum:[:n | n squared])         
     "
+
+    "Modified: / 23-08-2010 / 18:19:42 / cg"
 ! !
 
 !Collection methodsFor:'converting'!
@@ -2267,6 +2302,14 @@
     "
 !
 
+keysDo:aBlock
+    "evaluate the argument, aBlock for every key in the collection."
+
+    self keysAndValuesDo:[:k :v | aBlock value:k]
+
+    "Created: / 24-08-2010 / 10:12:14 / cg"
+!
+
 map:selector
     "for lisp fans - similar to collect"
 
@@ -3167,6 +3210,32 @@
     "Modified: / 11-07-2010 / 17:05:25 / cg"
 !
 
+maxApplying:aBlock
+    "return the maximum value from applying aBlock to each element in the receiver collection,
+     using < to compare elements.
+     Raises an error, if the receiver is empty."
+
+    self emptyCheck.
+
+    ^ self 
+        inject:nil
+        into:[:maxSoFar :this | 
+            |v|
+
+            v := aBlock value:this.
+            (maxSoFar isNil or:[maxSoFar < v]) 
+                ifTrue:[v]
+                ifFalse:[maxSoFar]
+        ]
+
+    "
+     #(15 1 -9 -20 10 5) max                        -> 15
+     #(15 1 -9 -20 10 5) maxApplying:[:el | el abs] -> 20
+    "
+
+    "Created: / 23-08-2010 / 11:02:50 / cg"
+!
+
 min
     "return the minimum value in the receiver collection,
      using < to compare elements.
@@ -3192,6 +3261,32 @@
     "Modified: / 11-07-2010 / 17:06:38 / cg"
 !
 
+minApplying:aBlock
+    "return the minimum value from applying aBlock to each element in the receiver collection,
+     using < to compare elements.
+     Raises an error, if the receiver is empty."
+
+    self emptyCheck.
+
+    ^ self 
+        inject:nil
+        into:[:minSoFar :this |
+            |v|
+
+            v := aBlock value:this.
+            (minSoFar isNil or:[v < minSoFar]) 
+                ifTrue:[v]
+                ifFalse:[minSoFar]
+        ]
+
+    "
+     #(15 -1 -9 10 5) min                        -> -9
+     #(15 -1 -9 10 5) minApplying:[:el | el abs] -> 1
+    "
+
+    "Created: / 23-08-2010 / 11:01:42 / cg"
+!
+
 minMax
     "return the minimum and maximum values in the receiver collection
      as a two element array, using #< to compare elements.
@@ -3736,15 +3831,15 @@
 !Collection class methodsFor:'documentation'!
 
 version
-    ^ '$Id: Collection.st 10564 2010-08-10 08:55:15Z vranyj1 $'
+    ^ '$Id: Collection.st 10570 2010-08-26 10:12:57Z vranyj1 $'
 !
 
 version_CVS
-    ^ 'Header: /cvs/stx/stx/libbasic/Collection.st,v 1.246 2010/08/07 17:18:25 cg Exp '
+    ^ 'Header: /cvs/stx/stx/libbasic/Collection.st,v 1.250 2010/08/24 15:10:11 cg Exp '
 !
 
 version_SVN
-    ^ '$Id: Collection.st 10564 2010-08-10 08:55:15Z vranyj1 $'
+    ^ '$Id: Collection.st 10570 2010-08-26 10:12:57Z vranyj1 $'
 ! !
 
 Collection initialize!
@@ -3752,3 +3847,4 @@
 
 
 
+