-- Functions on size-change graphs

hasArc :: Eq b => SizeChangeGraph a b -> SCArc b -> Bool
hasArc (_, arcs, _) arc = any (== arc) arcs
hasArc :: Eq b => SizeChangeGraph a b -> SCArc b -> Bool
hasArc (_, arcs, _) arc = any (== arc) arcs
hasArc (_, arcs, _) arc = any (== arc) arcs