add filter repr and restore reset iterator when filter added.

music21/stream/filter.py

@@ -37,6 +37,16 @@ def __init__(self):
     #def reset(self):
     #    pass
 
+    def _reprHead(self):
+        '''
+        returns a head that can be used with .format() to add additional
+        elements.
+        
+        >>> stream.filter.StreamFilter()._reprHead()
+        '<music21.stream.filter.StreamFilter {0}>'
+        '''
+        return '<{0}.{1} '.format(self.__module__, self.__class__.__name__) + '{0}>'
+
 
 class IsFilter(StreamFilter):
     derivationStr = 'is'
@@ -138,7 +148,8 @@ class ClassFilter(StreamFilter):
 
     >>> sI.filters.append(stream.filter.ClassFilter('Note'))
     >>> sI.filters
-    [<music21.stream.filter.ClassFilter object at 0x...>]
+    [<music21.stream.filter.ClassFilter Note>]
+    
     >>> for x in sI:
     ...     print(x)
     <music21.note.Note C>
@@ -154,10 +165,23 @@ def __init__(self, classList=()):
             classList = (classList,)
 
         self.classList = classList
+
+    def __eq__(self, other):
+        if other.__class__ is not self.__class__:
+            return False
+        if self.classList != other.classList:
+            return False
+        return True
 
     def __call__(self, item, iterator):
         return item.isClassOrSubclass(self.classList)
 
+    def __repr__(self):
+        if len(self.classList) == 1:
+            return self._reprHead().format(str(self.classList[0]))
+        else:
+            return self._reprHead().format(str(self.classList))
+
 
 class ClassNotFilter(ClassFilter):
     '''
@@ -171,7 +195,8 @@ class ClassNotFilter(ClassFilter):
 
     >>> sI.filters.append(stream.filter.ClassNotFilter('Note'))
     >>> sI.filters
-    [<music21.stream.filter.ClassNotFilter object at 0x...>]
+    [<music21.stream.filter.ClassNotFilter Note>]
+    
     >>> for x in sI:
     ...     print(x)
     <music21.note.Rest rest>

music21/stream/iterator.py

@@ -302,7 +302,9 @@ def matchingElements(self):
         <music21.stream.iterator.StreamIterator for Part:tn3/4 @:0>
         >>> sI.notes is sI
         True
-
+        >>> sI.filters
+        [<music21.stream.filter.ClassFilter NotRest>]
+        
         >>> sI.matchingElements()
         [<music21.note.Note C>, <music21.note.Note D>, 
          <music21.note.Note E>, <music21.note.Note F>, <music21.note.Note G>, 
@@ -529,13 +531,14 @@ def addFilter(self, newFilter):
         '''
         adds a filter to the list.
         
-        resets caches -- do not add filters any other way
-        
-        # TODO: support remove filter.
+        resets caches -- do not add filters any other way        
         '''
-        if newFilter not in self.filters:
-            self.filters.append(newFilter)
+        for f in self.filters:
+            if newFilter == f:
+                return self
+        self.filters.append(newFilter)
 
+        self.resetCaches()
         return self
 
     def removeFilter(self, oldFilter):