For debugging purposes, there's Debug.Trace, which does IO and subverts the type system to do so.
But with Haskell, I tend to do less debugging anyway, and more time getting the types right to with; when there's a function that doesn't work but still type checks, I feed it different inputs in GHCi and reread the code until I figure out why, and this is easy because almost all functions are pure and have no side effects and no reliance on global state. This is probably a sign that I don't write enough tests from the start, so I end up doing it like this.
But, I agree that doing things in a pure functional manner like this can make Haskell feel clunkier to program, even as other things feel easier and more graceful. Logging is one of those things where you wonder if the juice is worth the squeeze when it comes to doing everything in a pure functional way. Like I said, I haven't used it in a long time, and it's partly because of stuff like this, and partly because there's usually a language with a better set of libraries for the task.
> Logging is one of those things where you wonder if the juice is worth the squeeze
Yeah, because it's often not just for debugging purposes. Often you want to trace the call and its transformations through the system and systems. Including externally provided parameters like correlation ids.
Carrying the entire world with you is bulky and heavy :)
But with Haskell, I tend to do less debugging anyway, and more time getting the types right to with; when there's a function that doesn't work but still type checks, I feed it different inputs in GHCi and reread the code until I figure out why, and this is easy because almost all functions are pure and have no side effects and no reliance on global state. This is probably a sign that I don't write enough tests from the start, so I end up doing it like this.
But, I agree that doing things in a pure functional manner like this can make Haskell feel clunkier to program, even as other things feel easier and more graceful. Logging is one of those things where you wonder if the juice is worth the squeeze when it comes to doing everything in a pure functional way. Like I said, I haven't used it in a long time, and it's partly because of stuff like this, and partly because there's usually a language with a better set of libraries for the task.