Taking a wild guess at the source of the confusion, I should be clear that I love Haskell. It’s great for a lot of what I personally end up coding, namely math things that are non-heavy by computer standards but way too heavy to solve by hand. This isn’t naysaying.

I mean, you’re not going to be using an SQL database most likely for either of those applications (I realize I assumed that was obvious when talking about transactions, but perhaps that was a mistake to assume), so it’s not really applicable.

To be clear, I was introducing two new examples where I think this problem would come up. It could be that I’m missing something, but I’ve had this exchange a few times and been unimpressed by the solutions offered. The IO in those cases could get pretty spaghetti-ish. At that point, why not just use a state?

Like, using a list, which is a monad, you could code a Turing machine, and it could have a tape specifying literally anything. I can’t imagine that one would ever come up, though.

Ironically, I actually probably wouldn’t use Haskell for heavy data processing tasks, namely because Python has such an immense ecosystem for it (whether or not it should is another matter

It certainly is, haha. If it’s heavy Python is just calling Fortran, C or Rust anyway.