fix formula generator

scripts/formula_generator.py

@@ -127,15 +127,15 @@ def check_explored_states(model_name, model_instance, formula, time_out,
 
     # timeout or error found
     if (ltsmin_out is None):
-        return None
+        return False
 
     match_regex_explored = re.search(r'Explored (\d+) states', ltsmin_out)
 
     if match_regex_explored:
         nb_explored_states = int(match_regex_explored.group(1))
-        return nb_explored_states
+        return nb_explored_states >= min_explored_states
 
-    return ltsmin_out
+    return False
 
 
 def get_default_paths():
@@ -205,10 +205,10 @@ def generate_formulas(model_name,
         if (is_satisfied is None):
             continue
 
-        print(
-            "# explored states: ",
-            check_explored_states(model_name, model_instance, f, timeout,
-                                  min_explored_states, paths))
+        # if number of explored states is not satisfied
+        if not check_explored_states(model_name, model_instance, f, timeout,
+                                     min_explored_states, paths):
+            continue
 
         # add to formulas satisfied
         if is_satisfied and len(true_formulas) < n: