One thing I do wonder about is using Fibonacci to teach memoization in Haskell; like, the memoized fib, while still suboptimal compared to matrix-based or Binet-fib, is still relatively simple (use zipWith).
Fibonacci is the standard memoization example, though.
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A question I’m floating is whether Haskell is fun for DSA in general; as in, you can do imperative algorithms with IORef / concurrency mutables and ST monad, you can do functional algorithms with just pure code.
One thing I encountered was that someone was teaching Haskell recursion with quadtrees, but somehow a ton of the students missed recursion in their DSA class and couldn’t grok it.
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I’m not big on Haskell as a “pure”, in the vulgar sense, functional language; stuff like using accumulating parameters to simulate local variables makes sense in the same way Scheme in SICP taught recursion and iteration at the same time using accumulating parameters.
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Lastly, re OOP, Scheme was used as a general purpose teaching language for a while simply because it was fully multi-paradigm. Haskell is functional by default, monadic by design, meaning that it supports both functional and imperative paradigms, and LogicT adds logic programming, but the poor OOP libs mean that it can’t be used as a full multi-paradigm GP teaching language, because you can’t introduce OOP as necessary.
Even though a lot of people coming in to Haskell hate OOP, it’s still a dominant paradigm that FRP cannot yet fully replace, and thus worth teaching. Also, the FP jobs space is terrible, so OOP is still useful because tons of kids are going to graduate and become Java or .NET devs.