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Switching from C++ to Rust

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Re: Switching from C++ to Rust

#51

Post by howinteresting »

burntsushi wrote: post #3

The call out to sum types is something I feel. I've been using Rust daily for almost 10 years now, and sum types are absolutely still one of the things I love most about it. It's easily one of the things I miss the most in other languages that don't have them. I'm usually a proponent of "using languages as they're intended," but I missed exhaustiveness checking so much that I ported a version of it to Go[1] as a sort…

I'm going to make the even stronger claim that a general-purpose statically typed language that doesn't support sum types and exhaustive pattern matching to at least the extent that Rust does is unfit for general use, just like a language that doesn't have product types is unfit for general use.

Dynamically-typed languages often have adhoc sum types.

Re: Switching from C++ to Rust

#52

Post by edgyquant »

zabzonk wrote: post #19
burntsushi wrote: post #3

The call out to sum types is something I feel. I've been using Rust daily for almost 10 years now, and sum types are absolutely still one of the things I love most about it. It's easily one of the things I miss the most in other languages that don't have them. I'm usually a proponent of "using languages as they're intended," but I missed exhaustiveness checking so much that I ported a version of it to Go[1] as a sort…

so, um, unions? i have to say that in many years of programming, i have almost never needed to use such types.

I can’t imagine not having the ability for a variable to be one of multiple potential types. I could probably work around it, sure, but why would you want to?

Re: Switching from C++ to Rust

#53

Post by burntsushi »

raincole wrote: post #45
burntsushi wrote: post #3

The call out to sum types is something I feel. I've been using Rust daily for almost 10 years now, and sum types are absolutely still one of the things I love most about it. It's easily one of the things I miss the most in other languages that don't have them. I'm usually a proponent of "using languages as they're intended," but I missed exhaustiveness checking so much that I ported a version of it to Go[1] as a sort…

> I've been using Rust daily for almost 10 years now, I'm just nitpicking but Rust is 7 years old and 7 doesn't feel almost 10... Edit: Rust hit 1.0 7 years ago. Now I feel silly.

Yeah as other have mentioned, I was using Rust before 1.0.

This is my first public commit: https://github.com/BurntSushi/quickcheck/commit/c9eb2884d6a6...

I didn't write any substantive Rust before that point. So I'm at over 9 years.

Re: Switching from C++ to Rust

#54

Post by cmrdporcupine »

zabzonk wrote: post #19
burntsushi wrote: post #3

The call out to sum types is something I feel. I've been using Rust daily for almost 10 years now, and sum types are absolutely still one of the things I love most about it. It's easily one of the things I miss the most in other languages that don't have them. I'm usually a proponent of "using languages as they're intended," but I missed exhaustiveness checking so much that I ported a version of it to Go[1] as a sort…

so, um, unions? i have to say that in many years of programming, i have almost never needed to use such types.

The C++ (or Java etc) way to do many of the kind of things people do with Rust pattern matching & sum types would be via OO subtyping polymorphism. e.g. classic visitor pattern, etc. Way more verbose and awkward, and scatters the logic all over the place.

Enums + switch is the other, and far less powerful.

Re: Switching from C++ to Rust

#55

Post by raincole »

burntsushi wrote: post #53
raincole wrote: post #45

Earlier quoted context omitted.

> I've been using Rust daily for almost 10 years now, I'm just nitpicking but Rust is 7 years old and 7 doesn't feel almost 10... Edit: Rust hit 1.0 7 years ago. Now I feel silly.

Yeah as other have mentioned, I was using Rust before 1.0. This is my first public commit: https://github.com/BurntSushi/quickcheck/commit/c9eb2884d6a6... I didn't write any substantive Rust before that point. So I'm at over 9 years.

oh I see. Sorry I didn't expect you're such an early adopter.

Edit: Oh uh you're burntsushi. Should've checked your username.

Re: Switching from C++ to Rust

#56

Post by nicoburns »

jcranmer wrote: post #40
epage wrote: post #25

Earlier quoted context omitted.

To me its not just exhaustiveness but that sum types (enums) are just like product types (structs), they have have member methods, implement traits, etc. Coming from C++, when I realized Rust let me do that, it blew me away.

A union in C++ is the same thing as a struct, except all of its fields live at the same offset. So you can define any method you want on it, including special stuff like constructors and destructors. No base classes are allowed, though.

A method on a union is much less useful when you can't match on the tag though. I suppose you could store tag inside the union. Is that common? I've always imagined C/C++ tagged unions would store tag outside the union.

Re: Switching from C++ to Rust

#57

Post by nightpool »

raincole wrote: post #45
burntsushi wrote: post #3

The call out to sum types is something I feel. I've been using Rust daily for almost 10 years now, and sum types are absolutely still one of the things I love most about it. It's easily one of the things I miss the most in other languages that don't have them. I'm usually a proponent of "using languages as they're intended," but I missed exhaustiveness checking so much that I ported a version of it to Go[1] as a sort…

> I've been using Rust daily for almost 10 years now, I'm just nitpicking but Rust is 7 years old and 7 doesn't feel almost 10... Edit: Rust hit 1.0 7 years ago. Now I feel silly.

The person you're replying to, BurntSushi, is one of the most well-known Rust library authors and has been publishing open source Rust code since (at least) March of 2014, when the initial commits on the old regex crate were recorded. That's 9 years, just based off of a random quick Github search, which was hardly exhaustive.

Re: Switching from C++ to Rust

#58

Post by riceart »

raincole wrote: post #45
burntsushi wrote: post #3

The call out to sum types is something I feel. I've been using Rust daily for almost 10 years now, and sum types are absolutely still one of the things I love most about it. It's easily one of the things I miss the most in other languages that don't have them. I'm usually a proponent of "using languages as they're intended," but I missed exhaustiveness checking so much that I ported a version of it to Go[1] as a sort…

> I've been using Rust daily for almost 10 years now, I'm just nitpicking but Rust is 7 years old and 7 doesn't feel almost 10... Edit: Rust hit 1.0 7 years ago. Now I feel silly.

If you’re going to nitpick you better be right, and you’re not. - and I think he might be too humble to say anything but you might want to look into who you’re replying to and their body of work.

Rust has been around for well over a decade - the first “stable” release was 7 years ago. It’s always been opensource - any random hacker could download it and start using it since it was available. I think you will find kind quite a few people on this site that took it for a spin when it was still under development.

I have nowhere near the credits of BurntSushi, and even I was dabbling with rust more than 7 years ago.

Don’t be a reply guy.

Re: Switching from C++ to Rust

#59

Post by zabzonk »

nicoburns wrote: post #46
zabzonk wrote: post #19

Earlier quoted context omitted.

so, um, unions? i have to say that in many years of programming, i have almost never needed to use such types.

Does your code ever contain class hierarchies with a fixed set of classes? Or variables where certain values have special case meaning? Those are the cases where Sum Types make things immeasurably nicer than the alternatives.

> Does your code ever contain class hierarchies with a fixed set of classes?

no - one of the advantages of OO programing is that class hierarchies (should you feel the need to use them, which mostly i do not) can be expanded. or indeed contracted.

> Or variables where certain values have special case meaning?

very, very rarely (i would say never, in my own code) but of course we have the null pointer as a counter-example. to which i can say: don't use raw pointers.

Re: Switching from C++ to Rust

#60

Post by ryandrake »

staunton wrote: post #17
est31 wrote: post #15

Earlier quoted context omitted.

You are still "managing" it even in that instance (just like in Rust). The overhead is just smaller than in say C or old style C++ with new/delete.

The overhead is the same. Rust just takes care that you're doing it right, while C++ lets you shoot your foot off in this area.

I know this is an unpopular opinion but if you want to stick with C++, the solution to this, at least in my experience, is to stop doing things that let you shoot your foot off. C++ gives you every tool in the tool chest, and most of them are not safe. Stick to a safe subset and you've solved 90% of all those stereotypically C++ problems.

I've got a pretty big C++ codebase for my hobby projects, sanded down, polished and perfected over the years without the usual corporate pressure to ship. The few times I run into memory corruption, a memory leak, a segfault, dereferencing a shit pointer, undefined behavior, and so on, its always, always because I'm doing something I shouldn't be doing. Like working with raw pointers or pointers to pointers to pointers, or traversing an array of bytes to do something there's already a library that does, or manually calling delete on something, or using reinterpret_cast, or using one of the many footguns C++ happily gives me. The simple key is to just stop doing these unnecessary things.

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