sort -bytestring +fgl

heapsort :: Ord a => [a] -> [a]
fgl Data.Graph.Inductive.Internal.Heap
topsort :: Graph gr => gr a b -> [Node]
fgl Data.Graph.Inductive.Query.DFS
topsort' :: Graph gr => gr a b -> [a]
fgl Data.Graph.Inductive.Query.DFS