diff --git a/logics/bags.py b/logics/bags.py
index 30ef358..b69d694 100644
--- a/logics/bags.py
+++ b/logics/bags.py
@@ -1,15 +1,18 @@
 from enum import Enum
-BagDesc_oper = Enum('BagDesc_oper', 'entity true l_and l_or l_not lt le eq ge gt')
+BagDesc_oper = Enum(
+    'BagDesc_oper', 'entity true l_and l_or l_not lt le eq ge gt')
+
 
 class BagDescription(object):
-    def __init__(self, f_type, L_oper = None, R_oper = None, entity = ""):
+
+    def __init__(self, f_type, L_oper=None, R_oper=None, entity=""):
         self.f_type = f_type
         self.left_operand = L_oper
         self.right_operand = R_oper
         self.entity = entity
-        
+
         self.sanity_check()
-        
+
     def __repr__(self):
         if self.f_type == BagDesc_oper.entity:
             return self.entity
@@ -31,45 +34,48 @@ class BagDescription(object):
             return repr(self.left_operand) + " >= " + repr(self.right_operand)
         if self.f_type == BagDesc_oper.gt:
             return repr(self.left_operand) + " > " + repr(self.right_operand)
-            
+
     def sanity_check(self):
         """Sanity checks"""
 
         for operand in (self.left_operand, self.right_operand):
             if operand:
-                if not (isinstance(operand, BagDescription) or isinstance(operand, int)):
-                    raise RuntimeError("Unexpected operand type for a bag: " + str(operand))
-        
+                if not(
+                        isinstance(operand, BagDescription)
+                        or isinstance(operand, int)):
+                    raise RuntimeError(
+                        "Unexpected operand type for a bag: " + str(operand))
+
     @classmethod
     def f_entity(cls, entity_name):
-        return cls(BagDesc_oper.entity, entity = entity_name)
-        
+        return cls(BagDesc_oper.entity, entity=entity_name)
+
     @classmethod
     def f_TRUE(cls):
         return cls(BagDesc_oper.true)
-        
+
     def __lt__(self, other):
-        return BagDescription(BagDesc_oper.lt, L_oper = self, R_oper = other)
-        
+        return BagDescription(BagDesc_oper.lt, L_oper=self, R_oper=other)
+
     def __le__(self, other):
-        return BagDescription(BagDesc_oper.le, L_oper = self, R_oper = other)
-        
+        return BagDescription(BagDesc_oper.le, L_oper=self, R_oper=other)
+
     def __eq__(self, other):
-        return BagDescription(BagDesc_oper.eq, L_oper = self, R_oper = other)
-    
+        return BagDescription(BagDesc_oper.eq, L_oper=self, R_oper=other)
+
     def __ge__(self, other):
-        return BagDescription(BagDesc_oper.ge, L_oper = self, R_oper = other)
-    
+        return BagDescription(BagDesc_oper.ge, L_oper=self, R_oper=other)
+
     def __gt__(self, other):
-        return BagDescription(BagDesc_oper.gt, L_oper = self, R_oper = other)
-        
+        return BagDescription(BagDesc_oper.gt, L_oper=self, R_oper=other)
+
     def __and__(self, other):
-        return BagDescription(BagDesc_oper.l_and, L_oper = self, R_oper = other)
-    
+        return BagDescription(BagDesc_oper.l_and, L_oper=self, R_oper=other)
+
     def __or__(self, other):
-        return BagDescription(BagDesc_oper.l_or, L_oper = self, R_oper = other)
-    
+        return BagDescription(BagDesc_oper.l_or, L_oper=self, R_oper=other)
+
     def __invert__(self):
-        return BagDescription(BagDesc_oper.l_not, L_oper = self)
-        
+        return BagDescription(BagDesc_oper.l_not, L_oper=self)
+
 # EOF
diff --git a/logics/rsltl.py b/logics/rsltl.py
index e8bd959..83d61d1 100644
--- a/logics/rsltl.py
+++ b/logics/rsltl.py
@@ -3,22 +3,30 @@ from enum import Enum
 
 from logics.bags import *
 
-rsLTL_form_type = Enum('rsLTL_form_type', 'bag l_and l_or l_not l_implies t_globally t_finally t_next t_until t_release')
+rsLTL_form_type = Enum(
+    'rsLTL_form_type',
+    'bag l_and l_or l_not l_implies t_globally t_finally t_next t_until t_release')
+
 
 class Formula_rsLTL(object):
-    
-    def __init__(self, f_type, L_oper = None, R_oper = None, sub_oper = None, bag = None):
+
+    def __init__(
+            self, f_type, L_oper=None, R_oper=None, sub_oper=None, bag=None):
         self.f_type = f_type
         self.left_operand = L_oper
         self.right_operand = R_oper
         self.sub_operand = sub_oper
         self.bag_descr = bag
-        
+
+        if callable(sub_oper):
+            raise RuntimeError(
+                "sub_oper should not be a function. Missing () for {0}?".format(sub_oper))
+
         if isinstance(self.left_operand, BagDescription):
             self.left_operand = Formula_rsLTL.f_bag(self.left_operand)
         if isinstance(self.right_operand, BagDescription):
             self.right_operand = Formula_rsLTL.f_bag(self.right_operand)
-    
+
     def __repr__(self):
         if self.f_type == rsLTL_form_type.bag:
             return repr(self.bag_descr)
@@ -37,9 +45,15 @@ class Formula_rsLTL(object):
         if self.f_type == rsLTL_form_type.l_implies:
             return "( " + repr(self.left_operand) + " => " + repr(self.right_operand) + " )"
         if self.f_type == rsLTL_form_type.t_until:
-            return "( " + repr(self.left_operand) + " U[" + repr(self.sub_operand) + "] " + repr(self.right_operand) + " )"
+            return "( " + repr(
+                self.left_operand) + " U[" + repr(
+                self.sub_operand) + "] " + repr(
+                self.right_operand) + " )"
         if self.f_type == rsLTL_form_type.t_release:
-            return "( " + repr(self.left_operand) + " R[" + repr(self.sub_operand) + "] " + repr(self.right_operand) + " )"
+            return "( " + repr(
+                self.left_operand) + " R[" + repr(
+                self.sub_operand) + "] " + repr(
+                self.right_operand) + " )"
 
     @property
     def is_bag(self):
@@ -47,48 +61,51 @@ class Formula_rsLTL(object):
 
     @classmethod
     def f_bag(cls, bag_descr):
-        return cls(rsLTL_form_type.bag, bag = bag_descr)
+        return cls(rsLTL_form_type.bag, bag=bag_descr)
 
     @classmethod
     def f_And(cls, arg_L, arg_R):
-        return cls(rsLTL_form_type.l_and, L_oper = arg_L, R_oper = arg_R)
-    
+        return cls(rsLTL_form_type.l_and, L_oper=arg_L, R_oper=arg_R)
+
     @classmethod
     def f_Or(cls, arg_L, arg_R):
-        return cls(rsLTL_form_type.l_or, L_oper = arg_L, R_oper = arg_R)
-        
+        return cls(rsLTL_form_type.l_or, L_oper=arg_L, R_oper=arg_R)
+
     @classmethod
     def f_Implies(cls, arg_L, arg_R):
-        return cls(rsLTL_form_type.l_implies, L_oper = arg_L, R_oper = arg_R)
-        
+        return cls(rsLTL_form_type.l_implies, L_oper=arg_L, R_oper=arg_R)
+
     @classmethod
     def f_X(cls, sub, arg):
-        return cls(rsLTL_form_type.t_next, L_oper = arg, sub_oper = sub)
+        return cls(rsLTL_form_type.t_next, L_oper=arg, sub_oper=sub)
 
     @classmethod
     def f_G(cls, sub, arg):
-        return cls(rsLTL_form_type.t_globally, L_oper = arg, sub_oper = sub)
-    
+        return cls(rsLTL_form_type.t_globally, L_oper=arg, sub_oper=sub)
+
     @classmethod
     def f_U(cls, sub, arg_L, arg_R):
-        return cls(rsLTL_form_type.t_until, L_oper = arg_L, R_oper = arg_R, sub_oper = sub)
+        return cls(
+            rsLTL_form_type.t_until, L_oper=arg_L, R_oper=arg_R, sub_oper=sub)
 
     @classmethod
     def f_F(cls, sub, arg_L):
-        return cls(rsLTL_form_type.t_finally, L_oper = arg_L, sub_oper = sub)
+        return cls(rsLTL_form_type.t_finally, L_oper=arg_L, sub_oper=sub)
 
     @classmethod
     def f_R(cls, sub, arg_L, arg_R):
-        return cls(rsLTL_form_type.t_release, L_oper = arg_L, R_oper = arg_R, sub_oper = sub)
-        
+        return cls(
+            rsLTL_form_type.t_release, L_oper=arg_L, R_oper=arg_R,
+            sub_oper=sub)
+
     def __and__(self, other):
-        return Formula_rsLTL(rsLTL_form_type.l_and, L_oper = self, R_oper = other)
-    
+        return Formula_rsLTL(rsLTL_form_type.l_and, L_oper=self, R_oper=other)
+
     def __or__(self, other):
-        return Formula_rsLTL(rsLTL_form_type.l_or, L_oper = self, R_oper = other)
-    
+        return Formula_rsLTL(rsLTL_form_type.l_or, L_oper=self, R_oper=other)
+
     def __invert__(self):
-        return Formula_rsLTL(rsLTL_form_type.l_not, L_oper = self)
+        return Formula_rsLTL(rsLTL_form_type.l_not, L_oper=self)
 
 
-# EOF
\ No newline at end of file
+# EOF