C++ to Rust Phrasebook
cel.cs.brown.edu
C++ to Rust Phrasebook
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Re: C++ to Rust Phrasebook
#2Epic. This is really good.
Re: C++ to Rust Phrasebook
#3One of the common pitfalls I've seen in my time is someone writing a language they are familiar with in a language that just doesn't fit; trying to apply idioms that flow well with one language to another language where that's just not a good way to achieve the same ends.
An example I've seen a lot is a C thinker writing C++ classes with an init() function; sure, it works, but the C++ way is to do that in constructors. (All those about to start listing exceptions to that C++ idiom, please save it to the end, thanks!) The C thinker is still thinking about objects as "allocate memory, then set values" rather than the C++ way where allocation and initialisation are wrapped together into a single action (from the programmer's point of view).
So what are these pitfalls for a C++ thinker when writing Rust? This "phrasebook" is embracing the idea of taking a C++ way of thinking and applying it to Rust, which I'm sure will be fine for many situations, but what are the C++ phrases that are just the wrong way to do things in Rust?
Re: C++ to Rust Phrasebook
#4Inverting the original intent, this is great, learn how Rust improves certain things and use that to write better C++ if possible.
Re: C++ to Rust Phrasebook
#5One of the common pitfalls I've seen in my time is someone writing a language they are familiar with in a language that just doesn't fit; trying to apply idioms that flow well with one language to another language where that's just not a good way to achieve the same ends. An example I've seen a lot is a C thinker writing C++ classes with an init() function; sure, it works, but the C++ way is to do that in constructor…
A resource like this is a good place to discuss where the two languages are near and far. Of course there are going to be styles within each language that differ as much as the languages themselves.
Re: C++ to Rust Phrasebook
#6I will be using this to learn both Rust and C++ and see which one I like better.
Re: C++ to Rust Phrasebook
#7There are so many different flavours of C++ put there that this guide doesn’t exactly do itself the credit it deserves.
There are easy ways to implement stuff like enums with members in C++, just put an anonymous enum inside a class/struct, its possible but marked as not possible.
Likewise when discussing modules in rust while completely ignoring the existence of modules in C++ that is actually support by modern tooling.
There are other places where there are similar issues I have with the text (you can just add a compiler flag and get the same behaviour. Don’t even try and argue “but rust just does it out of the box”, I would need to rewrite my entire codebase vs just adding a few bits of text to my build system, these things are not equivalent)
They didn’t discuss much about FFI at all, generally sayings “theres a crate for that and if there isn’t let us know”, in my experience the crates are not amazing for esoteric things (anything graphics’s related, ffmpeg is another one) and are actually significantly more painful to use that just writing in a restricted version of C++.
Rust has a happy path, and they are broadening it incrementally, but theres is a lifetime of history before rust even existed in C++ that isn’t that easy to sweep under the rug.
Re: C++ to Rust Phrasebook
#8I will be using this to learn both Rust and C++ and see which one I like better.
I've taken a look, and it's definitely expecting you to know some C++. Or at least, it spends equal time on both, which means it can't warn you about the foot guns in c++.
Re: C++ to Rust Phrasebook
#9I will be using this to learn both Rust and C++ and see which one I like better.
I've taken a look, and it's definitely expecting you to know some C++. Or at least, it spends equal time on both, which means it can't warn you about the foot guns in c++.
It's definitely written from the perspective of someone who "knows C++". But I put that in quotes because there are (at least) two interpretations of that phrase. There's the person who doesn't know any C++ at all, and for that person, this is useless. But there's the person who knows a baseline of C++ but doesn't know modern C++, and they can use this as a way to modernize their C++ code while ignoring the Rust bits. But either way, yes, it doesn't warn you about C++ footguns (other than pointing you towards Rust <-;).
Re: C++ to Rust Phrasebook
#10Inverting the original intent, this is great, learn how Rust improves certain things and use that to write better C++ if possible.
Plenty of C++ practitioners who still intend to mostly write C++ after learning some Rust said it actually gave them useful insights they'll be applying in future C++
We can also see in the committee proposal papers "Rust does X" has for years now been a good comeback when you need to show that X is a realistic choice not just for languages like Python which may be less concerned about performance and incur a heavy runtime, a garbage collector, etc., but also a "real" language like C++. The paper which landed code.contains("FOO") in the C++ string handling code is an example, there's a long list of languages which do this but they made sure to mention Rust.