.. I would use it.

what is your use case? Can you extract test cases that could be used to validate correctness and complexity of an implementation? Specific question: assume the implementation gives you S = transitive-closure-of(R). Then what do you do with S (in your application)? Does Data.Graph (i.e., array of lists of successors) have the right structure? E.g., it is inefficient to test for membership in these lists. But lists are fine if you need to handle all successors anyway. Evaluation of (recursive) Datalog queries is another application area of transitive closure algorithms. (e.g., https://doi.org/10.1007/BF01264013 ) - J.