+type FlattenState = State.State ([App], [CondDef], SignalId)
+
+-- | Add an application to the current FlattenState
+addApp :: App -> FlattenState ()
+addApp a = do
+ (apps, conds, n) <- State.get
+ State.put (a:apps, conds, n)
+
+-- | Add a conditional definition to the current FlattenState
+addCondDef :: CondDef -> FlattenState ()
+addCondDef c = do
+ (apps, conds, n) <- State.get
+ State.put (apps, c:conds, n)
+
+-- | Generates a new signal id, which is unique within the current flattening.
+genSignalId :: FlattenState SignalId
+genSignalId = do
+ (apps, conds, n) <- State.get
+ State.put (apps, conds, n+1)
+ return n