Hello, in order to tune my brain to "functional thinking" I've decided to start writing some "real" programs. After having spent a couple of days figuring out how to translate an imperative algorithm into stateless haskell I beleive I've now managed a simple implementation of the DBSCAN clustering algorithm. http://privatepaste.com/e6bb4fb665 This code has several drawbacks (and probably it doesn't work correctly after all) but I would like to tune its performance. Obviously the code calls several functions multiply with the same arguments. Haskell, being stateless should thus always yield the same resuts, correct? In this case performing the same calculations multiply seems pointless. My question: How would you go about improving this code? In any imperative language I would simply cache distances/neighborhoods in a matrix. Obviously this is not what the way to go in haskell? Thank you very much