Added len to Span class, and added an is_valid method to date. is_valid similar to is_regular, but allows partial dates

svn: r11528

src/gen/lib/date.py

@@ -111,6 +111,9 @@ class Span:
             return False
         return self.diff_tuple > other.diff_tuple
 
+    def __len__(self):
+        return len(self.diff_tuple)
+
 
 #-------------------------------------------------------------------------
 #
@@ -904,6 +907,12 @@ class Date:
         """
         return self.modifier != Date.MOD_TEXTONLY
 
+    def is_valid(self):
+        """ 
+        Return true if any part of the date is valid.
+        """
+        return self.modifier != Date.MOD_TEXTONLY and self.sortval != 0
+
     def get_stop_year(self):
         """
         Return the day of the year associated with the second part of a