might error when retracting a BC rule.

diff --git a/src/Dyna/Backend/Python/interpreter.py b/src/Dyna/Backend/Python/interpreter.py
index 19dfd5d57e56a440a63357648b57c02c01412c3c..87dcbb1651016abdafab6443a953933c18baecd3 100644 (file)
--- a/src/Dyna/Backend/Python/interpreter.py
+++ b/src/Dyna/Backend/Python/interpreter.py
@@ -350,7 +350,11 @@ class Interpreter(object):
                     def _emit(item, val, ruleix, variables):
                         item.aggregator.dec(val, ruleix, variables)
 
-                    rule.query(*head.args, emit=_emit)
+                    try:
+                        rule.query(*head.args, emit=_emit)
+                    except (TypeError, ZeroDivisionError):
+                        pass
+
                     self.agenda[head] = time()
 
         return self.go()