Composing monads is another one of those painful parts of haskell. I remember being so frustrated while learning Haskell that there was all of this "stuff" to learn to "use monads" but it seemd to not have anything to _do_ with `Monad`, and people told me what I needed to know was `Monad`. Someday I wanna write all that advice I wish I had received when learning Haskell. A _lot_ of it will be about dealing with general monad "stuff".
The thing that frustrated me in Rust coming from something like Ruby was how frequently I could not _do_ a very straightforward thing, because, for example, some function is a fnOnce instead of fnMulti, or the other way around, or whatever. Here's some of the experience from that time https://joelmccracken.github.io/entries/a-simple-web-app-in-.... It became clear to me eventually that some very minor changes in requirements could necessitate massive changes in how the whole data model is structured. Maybe eventually I'd get good enough at rust that this wouldn't be a huge issue, but I had no way of seeing how to get to that point from where I was.
In contrast, I can generally predict when some requirement is going to necessitate a big change in haskell: does it require a new side effect? if so, it may need a big change. If not, then it probably doesn't. But, I've found it surprisingly easy to make big changes from the nice type system.
I really don't get when rust folks claim "memory safety" like this; we've had garbage collection since 1959. Rust gives you memory safety with tight control over resource usage; memory safety is an advantage that Rust has over C or C++, but not over basically every other language people still talk about.
If you just clone/copy every data structure left and right, then you're at a _worse_ spot than with garbage collection/reference counting when it comes to memory usage. I _guess_ you are getting the ability to avoid GC pauses, but, why not use a reference counted language if that's the problem? copy/clone data all of the time can't be faster than the overhead from a reference counting, can it??
In haskell, I did find that once I understood the various pieces I needed to work with, actually solving problems (e.g. composing monads) is much easier. I don't generally have a hard time actually programming Haskell. All that effort is front-loaded though, and it can be hard to know exactly what you need to learn in order to understand some new unfamiliar thing.
Your preferring Rust over Haskell is totally fine BTW, I'm just trying to draw a distinction between something that's hard to _use_ vs something that's hard to _learn_. Many common languages are much harder to use IME; I feel like I have to think so hard all of the time about every line of code to make sure I'm not missing something, some important side effect that I don't know about that is happening at some function call. With Haskell, I can generally skim the code and find what's important quite quickly because of the type system.
I do plan to learn Rust at some point still whenever the planets align and I need to know something like it. Until then, there are so many other things that interest me, and not enough hours in the day. I still wonder if I have really missed out on some benefit from learning to think more about data ownership in programs.
