Comment by jgilias | Hacker News Reader

Comment by jgilias | Hacker News Reader

Parent Full thread

I've done my share of C++ and now Rust, and I don't really get why people keep saying that Rust is a 'cleaned-up C++'. In my opinion this couldn't be further from my subjective truth. I see C++ as an effort to extend C to enable object oriented programming patterns. And everything else being added to it as more and more people have come to appreciate patterns from other programming paradigms. But fundamentally C++ to me is still 'C with classes'.

Whereas Rust, to me at least, is 'ML-ish with curly braces'. So, a language firmly based in the ML heritage with C-like syntax. So, fundamentally working with types and 'typeclasses' and heavily leaning towards filter/map/fold/reduce/lift/unlift type of thinking. Sure, throwing funtions around as first class objects are not as easy or straightforward as it is in 'real FP' languages, but that's a trade-off I'm willing to take for the guarantees that Rust provides.

I'm genuinely curious what's the reasoning behind being able to assert that 'Rust is a cleaned-up C++'.

Rust is rather more like "Haskell-ish C++". (Typeclasses were popularized by Haskell and are not available in SML or OCaml.) While the C++ heritage is obviously the memory management – no runtime, heavy use of scope based deterministic destruction ("RAII"). Also the compile-time metaprogramming that gets monomorphized. (All those template/generic instantiations that can bloat the binaries if overused :D)

I've been bashed before for saying something along the lines of "Haskell-ish C++". Their fair point being that the only Haskell influence is the typeclasses, and all other ML-influences are just ML-influences that are not unique to Haskell. Fair enough :)

For reference, here's the "influences" page of the Rust reference: https://doc.rust-lang.org/reference/influences.html

SML, OCaml, C++ and Haskell are all mentionned.

Have you not seen much modern C++? If you are used to this style of C++, Rust is a very obvious variant of it, but with more static guarantees with regards to safety. Working heavily with types has been common in C++ for a couple decades now, and there are libraries with bring in filter/map/fold/reduce/lift/unlift style.

The code I've had to work with was definitely more on the OOP paradigm side. Can you provide an example project with a more 'modern' C++ code base that I could check out?

You're doing the comparison from the bottom-up, perhaps like how a programming language connoisseur would look at them -- how the linguistic features of C++ and Rust were constructed -- while I'm looking at them from the top down, how just a programmer who doesn't particularly care about PL theory would: what is their design philosophy? Both are low-level languages (so, low-abstraction), which try hard through various syntactical techniques and a nice dose of implicitness to make code, once written, appear high-level on the page. I find those two languages almost indistinguishable in terms of "feel." It doesn't feel like Python, it doesn't feel like Java or Go, and it doesn't feel like C; it feels like C++.

I do agree that Rust 'feels' more like C++ than Python or Java. But then, from my limited experience with dabbling into Haskell, to me it feels more like Haskell than C++. In Rust, from the language perspective, I have to deal with things like these:

- Doing Option<T> -> Option<U>

- At what point do I do Option<T> -> Result<T>

- Should I transpose Vec<Option<T>> to Option<Vec<T>> now or later?

- Often reaching for algebraic data types

- How to map over this to collect it into what I need

- Ah, it needs to implement Hash, Eq, PartialEq ... SomeTrait to make it work the way I want

- Pattern matching all over the place

All of which to me mentally feels more like something along the lines of F#, OCaml or Haskell than C++ that 'normal people write'.

Because people know C++ but don't know ML.

Depends on the people.

When I did my degree, C++ was taught in the second year and Caml Light in the third.

It's like C++ is a gas-powered chainsaw and Rust is a newfangled electric "smart" chainsaw.

I often use "table saw" when making this sort of analogy, because there's even a more direct comparison: https://www.sawstop.com/

(As an aside, WOW! What a great invention! The folks who sent in pictures of their tiny cuts (instead of severed fingers) nearly made me cry.)

That's a brilliant metaphor to drive home the safety advantages of Rust! "It's a table saw that won't chop off your fingers!"

That's a "shut up and take my money" proposition. (And it helps that it's a really good table saw too.)

(As another aside, I got to the testimonial from an employer talking about the peace of mind of knowing the workers on the shop floor are safe and it "clicked" for me: you've got metrics and liability for job site safety so you can quantify that peace of mind. We still not there with software quality liability eh?)

Reminds me that unprofitable hotness electric car company whose core business is to manipulate both balance sheet and government.

Reply on news.ycombinator.com