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Cake day: August 18th, 2023

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  • [warning: “annoying Rust guy” comment incoming]

    I don’t think Rust is perfect, but arguably I do “idolize” it, because I genuinely think it’s notably better both in design and in practice than every other language I’ve used. This includes:

    • C
    • C++
    • Java
    • C#
    • Kotlin
    • Scala
    • Python
    • Ruby
    • JavaScript (…I’ve barely used this, but I doubt my opinion would change on this one)
    • Perl
    • Go
    • Bash (…look, I’ve had to write actual nontrivial scripts with loops and functions, so yes, Bash is a real language; it just sucks)
    • Tcl/Tk (if you don’t know, don’t ask)
    • CommonLisp (…again, I’ve barely used this, and I wish I had more experience with this and other Lisps)

    In a literal sense, I agree that all (practical) languages “are flawed.” And there are things I appreciate about all of the above languages (…except Tcl/Tk), even if I don’t “like” the language overall. But I sincerely believe that statements like “all languages are flawed” and “use the best tool for the job” tend to imply that all (modern, mainstream) languages are equally flawed, just in different ways, which is absolutely not true. And in particular, it used to be true that all languages made tradeoffs between a fairly static, global set of binary criteria:

    • safety/correctness versus “power” (i.e. low-level system control)
    • safety/correctness versus run-time efficiency (both parallelism and high single-thread performance)
    • ease-of-use/ease-of-learning versus “power” and runtime-efficiency
    • implementation simplicity versus feature-richness
    • build-time versus run-time efficiency
    • type-safety versus runtime flexibility

    Looking at these, it’s pretty easy to see where most of the languages in my list above fall on each side of each of these criteria. What’s special about Rust is that the core language design prevents a relatively novel set of tradeoffs, allowing it to choose “both” for the first two criteria (though certainly not the latter three; the “ease-of-use” one is debatable) at the expense of higher implementation complexity and a steeper learning curve.

    The great thing about this isn’t that Rust has “solved” the problem of language tradeoffs. It’s that Rust has broadened the space of available tradeoffs. The assumption that safety necessarily comes at a runtime cost was so pervasive prior to Rust that some engineers still believe it. But now, Rust has proven, empirically, that this is not the case! And so my ultimate hope for Rust isn’t that it becomes ubiquitous; it’s that it inspires even better languages, or at least, more languages that use concepts Rust has brought to the mainstream (such as sum-types) as a means to explore new design tradeoff spaces. (The standard example here is a language with a lightweight garbage-collecting runtime that also has traits, sum-types, and correct-by-default parallelism.)

    There are other languages that, based on what I know about them, might inspire the same type of enthusiasm if I were to actually use them more:

    • Erlang
    • Gleam
    • OCaml
    • Swift

    …but, with the exception of Swift, these are all effectively “niche” languages. One notable thing about Rust is that its adoption has actually been rather astounding, by systems language standards. (Note that D and Ada never even got close to Rust’s popularity.)








  • Ah. Rust’s macros and the C preprocessor’s exist in vastly different universes. The C preprocessor is literally just a fancy programmatic copy-and-paste tool. Rust macros read the input source code and then execute other source code (the macro definition) to generate new source code that the compiler then reads.

    I love Rust, but Rust macros are arguably more of a footgun than compile-time reflection would be, and as amazing as serde is (and no, there’s nothing comparable in standard-compliant C++ yet), there’s a strong argument that compile-time reflection would be a preferable technique for deriving serialization, argument-parsing, and similar feature.











  • Whatever you want to call them, my point is that most languages, including Rust, don’t have a way to define new integer types that are constrained by user-provided bounds.

    Dependent types, as far as I’m aware, aren’t defined in terms of “compile time” versus “run time”; they’re just types that depend on a value. It seems to me that constraining an integer type to a specific range of values is a clear example of that, but I’m not a type theory expert.


  • It sounds like you’re talking about dependent typing, then, at least for integers? That’s certainly a feature Rust lacks that seems like it would be nice, though I understand it’s quite complicated to implement and would probably make Rust compile times much slower.

    For ordinary integers, an arithmetic overflow is similar to an OOB array reference and should be trapped, though you might sometimes choose to disable the trap for better performance, similar to how you might disable an array subscript OOB check.

    That’s exactly what I described above. By default, trapping on overflow/underflow is enabled for debug builds and disabled for release builds. As I said, I think this is a sensible behavior. But in addition to per-operation explicit handling, you can explicitly turn global trapping behavior trapping on or off in your build profile, though.