--- a/Collection.st	Wed Sep 14 11:54:01 2016 +0200
+++ b/Collection.st	Wed Sep 14 12:18:50 2016 +0200
@@ -1,3 +1,5 @@
+"{ Encoding: utf8 }"
+
 "
  COPYRIGHT (c) 1989 by Claus Gittinger
               All Rights Reserved
@@ -273,7 +275,6 @@
     ^ self newWithSize:n
 ! !
 
-
 !Collection class methodsFor:'Signal constants'!
 
 emptyCollectionSignal
@@ -333,6 +334,14 @@
      Abstract subclasses must redefine this again."
 
     ^ self == Collection
+!
+
+mutableClass
+    "Return a version of me with mutable instances.
+     Only redefined in the immutable collections (of which instances are
+     created by the compiler)"
+
+    ^ self
 ! !
 
 !Collection methodsFor:'Compatibility-ANSI'!
@@ -540,7 +549,6 @@
     "Created: / 22-10-2008 / 21:29:27 / cg"
 ! !
 
-
 !Collection methodsFor:'accessing'!
 
 anElement
@@ -4333,7 +4341,7 @@
     aStream nextPut:$)
 
     "
-     #(1 2 3 'hello' $a $ü) printOn:Transcript
+     #(1 2 3 'hello' $a $ü) printOn:Transcript
      (Array new:100000) printOn:Transcript
      (Array new:100000) printOn:Stdout
      (Array new:100000) printString size
@@ -5687,7 +5695,7 @@
 includesAll:aCollection
     "return true if the receiver includes all elements of
      the argument, aCollection; false if any is missing.
-     Notice: this method has O² runtime behavior and may be
+     Notice: this method has O² runtime behavior and may be
              slow for big receivers/args.
              Think about using a Set, or Dictionary."
 
@@ -5707,7 +5715,7 @@
      Return false if it includes none.
      Uses #= (value compare)
      Notice:
-        this method has O² runtime behavior for some subclasses and may be slow for big receivers/args.
+        this method has O² runtime behavior for some subclasses and may be slow for big receivers/args.
         Think about using a Set or Dictionary.
         Some speedup is also possible, by arranging highly
         probable elements towards the beginning of aCollection, to avoid useless searches.
@@ -5777,7 +5785,7 @@
      Return false if it includes none.
      Use identity compare for comparing.
      Notice:
-        this method has O² runtime behavior for some subclasses and may be slow for big receivers/args.
+        this method has O² runtime behavior for some subclasses and may be slow for big receivers/args.
         Think about using a Set or Dictionary.
         Some speedup is also possible, by arranging highly
         probable elements towards the beginning of aCollection, to avoid useless searches."
@@ -5993,7 +6001,6 @@
     ^ aVisitor visitCollection:self with:aParameter
 ! !
 
-
 !Collection class methodsFor:'documentation'!
 
 version