* @return True, if the contents of this statement list changed.
		 */
		public boolean retainAll(final Collection c) {
			boolean changed = false;

			if (c == this) {
				return false;
			}

			final Iterator iter = iterator();

			while (iter.hasNext()) {
				if (!c.contains(iter.next())) {
					changed = true;
					iter.remove();
				}
			}

			return changed;
		}