Maybe you mean using lazy evaluation as a memoization hack? That is a well known trick in Haskell though I agree it is in some ways cringy, relying on the eval

Maybe you mean using lazy evaluation as a memoization hack? That is a well known trick in Haskell though I agree it is in some ways cringy, relying on the evaluation strategy like that. But there are some Hackage packages that make it fairly convenient to use. I did a naive implementation myself and benchmarked it against an explicit STRef as a cache cell. I don't remember the result but it wasn't a huge (OOM+) difference iirc. Rather than using an array as the memo cache (which means you must know its size in advance), it's nicer to use an infinite branching tree.