Why is Rust difficult?

Rust is considered difficult to learn by many people. Indeed, when I learned it, I considered it to be the hardest programming language up to that time I’ve met. And that says something, since I have a habit of learning whatever language I find interesting. Looking back, I’m not sure I was correct, C++ is probably harder ‒ but it was distributed into much longer time than learning Rust.

So, this is my point of view what I believe are the reasons. Also, I’ll claim this upfront ‒ I don’t consider it necessarily a bad thing for a language to be hard to learn, not when I get something in return for the investment.

Rust attacks hard problems

There are languages that are simple. To point one of them, look at lua. The complete language manual is shorter than introductory book to most other languages. It has something like 4 or 5 data types and you can’t add your own. Why is it so?

Because lua, and other languages, made different choices about what their goals are. If you start designing a language with the intention of creating a very simple and minimal language, you will end up with a very simple and minimal language (if you’re any good at designing languages). The language may not be suitable in some situations, but that wasn’t the goal.

On the other hand, if you declare upfront that your language needs to be able to solve any hard problem anyone thinks of, run fast and be safe to use then you’ll probably get your wish, but it’ll hardly be simple.

And that’s what the authors of Rust decided. To be able to do whatever is needed done. But Rust is not the only complex language because of that. Look at C++ ‒ Rust at least keeps the complexity somewhat sane.

However, this is difficulty that anyone trying to enter the low-level world of system programming should expect. All these details about where a memory is allocated, how much memory it takes, that were not important in other languages suddenly surface. But that’s because you need the control, isn’t it? Otherwise, you would use the simple language, as it would be sufficient.

The language is honest

This is similar to the above, but not completely.

When the language designers want to solve a problem, there are two general approaches.

First one is to hide the problem from sight and let the language handle it somehow. The fact it isn’t always the best way doesn’t matter.

The other approach is being honest about the complexity of the problem, admit it, but arm the programmer with tools to handle it.

This means the beginner must grasp the complete complexity of the problem, but makes it easier in the long term ‒ simply because after solving the problems, there’s no beginner any more and because sometimes having the needed tools and not fighting the language to get to the problem is just easier.

Rust is different

One of the problems why I found Rust hard to learn was that it looked similar to other imperative languages on one side, but introduced a lot of novel concepts. It has all these cycles, conditions, functions, like everyone else. But it also has the ownerships and traits and lifetimes. These do have its reasons, but they feel alien at first ‒ but not alien enough to completely switch mental models. But that also make the language interesting.

What I mean about switching mental models. If you coded in Python and then tried Haskell, you’d see at the first glance than nothing is the same. But with Rust, I started to code like I did in C++, because it looked a bit like C++. Put some callbacks here and there… and then the compiler complained, because such model doesn’t fit. I tried to force it and after a time I got a really hairy API I didn’t like a bit.

The problem here is two-fold:

It is not clear upfront the language is different than whatever else one might already know and that the other knowledge needs to be put on a shelf for a while.

There are many books about good design in the OOP world, many books and classes how to structure a program in pure functional world. But not many (none?) books about best practices for a world based on ownership and composition.

The compiler is a very strict teacher

All things together, Rust insists that your program will be correct or it won’t compile. Strict typing makes you think about the relations in your program. It checks that you don’t get data races. It will tell you if you try to free some memory too soon.

This is a good thing. It makes sure your programs are better than of the competition (if you manage to compile them, of course), that they are less likely to crash and burn or something even worse. It makes the language easier to use (imagine if you had to actively think about all these things instead of relying on the compiler to check it for you ‒ welcome to C).

But at the same time, it makes learning it a bit harder, because it insists on you learning everything needed to write a good program. An average is not acceptable.

If you just learned about how to write a function, it doesn’t feel very encouraging when the compiler starts to talk about data races (what are these, anyway, you ask at the time). A program that is subtly wrong would be fine at that time ‒ at least it would run.

But in the long run this makes you a much better programmer. Even in other languages.

Today, there’s a lot of very good documentation about this ‒ it at least explains why such things are incorrect and how to fix them.

People say it’s hard

This one comes down to perception. If so many people say Rust is hard to learn, then it must be true. The fact they learned in times when there was no or little documentation doesn’t change a thing here.

What to do about it

Documentation and resources help a long way. However, I believe the biggest issue is perception and expectations.

So, if someone asks (or if you’re considering learning Rust and ask yourself): yes, Rust is hard to learn. But not necessarily slow to learn. A month or so of experimenting in the evenings after work goes a long way. By that time, you probably could start contributing to the Rust compiler itself, with some little help ‒ and compilers are one of the most complex pieces of software that exist.

What should a beginner in Rust expect: