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Spiritually it seems to be a replacement for C++. If you're using C++ for something, Rust seems like a well-thought-out C++. If you're using C for something,

Spiritually it seems to be a replacement for C++. If you're using C++ for something, Rust seems like a well-thought-out C++. If you're using C for something, then probably not, for the same reasons you are not using C++.

pcwalton 11y ago
If you're using C and encountering memory safety problems, however, then you may want to consider Rust. Moving to C++ from C offers a small safety benefit and a large expressiveness benefit at the cost of a very large complexity drawback. Moving to Rust from C, on the other hand, offers a large safety benefit and a large expressiveness benefit at the cost of a significant complexity drawback. (I think Rust as a language is less complex than C++, and the complexity of C/C++ undefined behavior rules completely vanishes in safe Rust.)
- dlanouette 11y ago
  Can you elaborate on what you mean by the "very large/significant complexity drawback"? From what I've seen (which is admittedly small) Rust is much less complex than either C or C++.
  - JoshTriplett 11y ago
    Rust is a larger language than C, though far smaller than C++. More importantly, with Rust you should expect to spend more of your time convincing the compiler that you've written correct code, which requires a reasonable understanding of Rust semantics. (The compiler makes that fairly easy, but it can still be a bit of a shock when you're staring at code that seems obviously correct to you but the compiler has no way to know that.) On the other hand, once you do convince the compiler, you have an excellent chance that the code actually is correct, and you'll spend far less time chasing down crazy runtime bugs.
    - selestify 11y ago
      > On the other hand, once you do convince the compiler, you have an excellent chance that the code actually is correct, and you'll spend far less time chasing down crazy runtime bugs. That's what I love about Haskell as well. Know of any other languages like this?
      - JoshTriplett 11y ago
        I used to feel more strongly that way about Haskell. I still do about most types of errors, but I spent a long time debugging serious performance issues caused by unbounded laziness and insufficient strictness. In general, I'm a big fan of static typing. I don't know any other language that manages to provide as much static memory safety as Rust, though; that's the main innovation in Rust.
        gue5t 11y ago
        The difficulty of reasoning about strictness and memory consumption in Haskell is by far its biggest flaw. This is why I stopped writing Haskell: even if you understand your own code perfectly, you can't tell how well-behaved it will be without reading your dependencies and all their dependencies. And yet strictness typing seems to be on nobody's plan for future Haskell extensions.
  - pcwalton 11y ago
    Compared to C, Rust has generics, closures, a module system, hygienic macros, real strings, slices, lifetimes, and the borrow checker. But note that all the features that Rust adds over C are, in my view, one of (a) necessary for memory safety (which is an important feature in 2015); (b) improvements on C features (macros compared to cpp, strings compared to char *, modules compared to #include); (c) things you expect from a modern language (generics, closures).
- ivoras 11y ago
  I'd say that Go is a better "better C" than Rust, for already functional C programmers. The syntax of Go is as removed from C as Rust's, and it's more mature. TBH, Rust looks a bit stillborn - too weird to live, too rare to die.
  - steveklabnik 11y ago
    This is also why it matters to know what you mean by C: to me, a key aspect of C is the manual memory management and lack of a runtime. A C that adds GC is no longer C.
  - MichaelGG 11y ago
    People say this. I looked into Go, to write modules for VoIP platforms. Go is a managed runtime environment. I can't drop it in where I'm currently using C. I can't easily start migrating pieces of a program to Go. But Rust does execute exactly where C can. In fact, I don't see how Go is C like at all. It seems much more akin to other managed languages, like Java. The only reason it seems to come up in these discussions is that Google said it was for "systems" programming, using a new value of "systems". Maybe you're referring to mindsets and syntax or something?
  - loudmax 11y ago
    I strongly disagree with this assessment. Go may be a better Java or Python, but as a GC'd language it's not in the same league as C or C++ or Rust. I also happen to prefer Go's syntax to Rust's, but I can live with GC'd performance. If I were writing something as performance critical as a browser rendering engine, I could get past the weird syntax. I think both Go and Rust have bright futures.
  - dragonwriter 11y ago
    Go is more mature than Rust, and to the extent that they have similar advantages (which I don't think is very much) Go's first-mover advantage may help it. OTOH, Rust is maturing quite well, and I think it has broader applicability and a very different area that is its strongest point that is the case for Go, so I think that its quite likely to do well initially in places where Go isn't much of a competitor, and in the long run may well be more successful than Go. (Particularly, its focus seems to be aimed at lower-level system programming than Go's, but a the same time it has constructs that, once good low-level libraries are in place, seem to make it potentially quite good for higher-level programming as well.)
pornel 11y ago
I'm using Rust as a C replacement (I need speed and ability to produce libraries with a C ABI). To me Rust is "C with templates". Rust isn't an OO language in the same style as C++ (instead of inheritance it has trait polymorphism, which is nice, but doesn't always map to C++ design patterns). I don't use C++, because for every thing that can be written in C++ there's always a more complex/clever version that should have been written instead.

pcwalton 11y ago

If you're using C and encountering memory safety problems, however, then you may want to consider Rust. Moving to C++ from C offers a small safety benefit and a large expressiveness benefit at the cost of a very large complexity drawback. Moving to Rust from C, on the other hand, offers a large safety benefit and a large expressiveness benefit at the cost of a significant complexity drawback. (I think Rust as a language is less complex than C++, and the complexity of C/C++ undefined behavior rules completely vanishes in safe Rust.)

dlanouette 11y ago
Can you elaborate on what you mean by the "very large/significant complexity drawback"? From what I've seen (which is admittedly small) Rust is much less complex than either C or C++.
- JoshTriplett 11y ago
  Rust is a larger language than C, though far smaller than C++. More importantly, with Rust you should expect to spend more of your time convincing the compiler that you've written correct code, which requires a reasonable understanding of Rust semantics. (The compiler makes that fairly easy, but it can still be a bit of a shock when you're staring at code that seems obviously correct to you but the compiler has no way to know that.) On the other hand, once you do convince the compiler, you have an excellent chance that the code actually is correct, and you'll spend far less time chasing down crazy runtime bugs.
  - selestify 11y ago
    > On the other hand, once you do convince the compiler, you have an excellent chance that the code actually is correct, and you'll spend far less time chasing down crazy runtime bugs. That's what I love about Haskell as well. Know of any other languages like this?
    - JoshTriplett 11y ago
      I used to feel more strongly that way about Haskell. I still do about most types of errors, but I spent a long time debugging serious performance issues caused by unbounded laziness and insufficient strictness. In general, I'm a big fan of static typing. I don't know any other language that manages to provide as much static memory safety as Rust, though; that's the main innovation in Rust.
      - gue5t 11y ago
        The difficulty of reasoning about strictness and memory consumption in Haskell is by far its biggest flaw. This is why I stopped writing Haskell: even if you understand your own code perfectly, you can't tell how well-behaved it will be without reading your dependencies and all their dependencies. And yet strictness typing seems to be on nobody's plan for future Haskell extensions.
- pcwalton 11y ago
  Compared to C, Rust has generics, closures, a module system, hygienic macros, real strings, slices, lifetimes, and the borrow checker. But note that all the features that Rust adds over C are, in my view, one of (a) necessary for memory safety (which is an important feature in 2015); (b) improvements on C features (macros compared to cpp, strings compared to char *, modules compared to #include); (c) things you expect from a modern language (generics, closures).
ivoras 11y ago
I'd say that Go is a better "better C" than Rust, for already functional C programmers. The syntax of Go is as removed from C as Rust's, and it's more mature. TBH, Rust looks a bit stillborn - too weird to live, too rare to die.
- steveklabnik 11y ago
  This is also why it matters to know what you mean by C: to me, a key aspect of C is the manual memory management and lack of a runtime. A C that adds GC is no longer C.
- MichaelGG 11y ago
  People say this. I looked into Go, to write modules for VoIP platforms. Go is a managed runtime environment. I can't drop it in where I'm currently using C. I can't easily start migrating pieces of a program to Go. But Rust does execute exactly where C can. In fact, I don't see how Go is C like at all. It seems much more akin to other managed languages, like Java. The only reason it seems to come up in these discussions is that Google said it was for "systems" programming, using a new value of "systems". Maybe you're referring to mindsets and syntax or something?
- loudmax 11y ago
  I strongly disagree with this assessment. Go may be a better Java or Python, but as a GC'd language it's not in the same league as C or C++ or Rust. I also happen to prefer Go's syntax to Rust's, but I can live with GC'd performance. If I were writing something as performance critical as a browser rendering engine, I could get past the weird syntax. I think both Go and Rust have bright futures.
- dragonwriter 11y ago
  Go is more mature than Rust, and to the extent that they have similar advantages (which I don't think is very much) Go's first-mover advantage may help it. OTOH, Rust is maturing quite well, and I think it has broader applicability and a very different area that is its strongest point that is the case for Go, so I think that its quite likely to do well initially in places where Go isn't much of a competitor, and in the long run may well be more successful than Go. (Particularly, its focus seems to be aimed at lower-level system programming than Go's, but a the same time it has constructs that, once good low-level libraries are in place, seem to make it potentially quite good for higher-level programming as well.)

pornel 11y ago

I'm using Rust as a C replacement (I need speed and ability to produce libraries with a C ABI). To me Rust is "C with templates". Rust isn't an OO language in the same style as C++ (instead of inheritance it has trait polymorphism, which is nice, but doesn't always map to C++ design patterns). I don't use C++, because for every thing that can be written in C++ there's always a more complex/clever version that should have been written instead.