Another thing to be learned down the Haskell rabbit-hole: Thinking in infinites. Today someone posed a puzzle which I tried to solve in a straight-forward, recursive manner: Building a list of primes. The requested algorithm was plain enough:
Create a list of primes “as you go”, considering a number prime if it can’t be divided by any number already considered prime.
However, although my straightforward solution worked on discrete ranges, it couldn’t yield a single prime when called on an infinite range — something I’m completely unused to from other languages, except for some experience with the SERIES library in Common Lisp.