bytestring VS cxx

The documentation is itself fairly funny, for those who don’t care to click ahead:

> This "function" has a superficial similarity to ‘unsafePerformIO’ but it is in fact a malevolent agent of chaos. It unpicks the seams of reality (and the IO monad) so that the normal rules no longer apply. It lulls you into thinking it is reasonable, but when you are not looking it stabs you in the back and aliases all of your mutable buffers. The carcass of many a seasoned Haskell programmer lie strewn at its feet.

> Witness the trail of destruction:

    https://github.com/haskell/bytestring/commit/71c4b438c675aa360c79d79acc9a491e7bbc26e7

If you bring in efficient strings from bytestring, densely packed arrays from vector, and an in-place sort from vector-algorithms, you can bring it down to 275ms (uses 19MB of mem).

bytestring

Note that this release is broken for Windows.

I've opened https://github.com/haskell/bytestring/issues/455 so the situation can be improved. You're very welcome to chime in on the discussion or to contribute some of the missing documentation yourself! :)

Highlights from the changelog:

Well, ByteString in particular should not have an IsString instance in a new report. That's pretty clear by https://github.com/haskell/bytestring/issues/140 : the concensus is that there is no good solution right now, but it should not have gotten an IsString instance in the first place. If a theoretical new Haskell Report 202x includes OverloadedStrings (as it should) to handle string literals analogously to numeric literals, I'd expect it to not give ByteString (which is really just a collection of octets) an IsString instance, with all it's issues and rattail due to the encoding question being implicitized.

Standard streaming libraries. They are being written by people that make the effort to understand performance and I have a hope that they make sure their streams run in linear space under any optimizations. It is curious and unsettling that we have standard lazy text and byte streams at the same time — and the default lazy lists, of course. I have been doing some work on byte streams and what I found out is that there is no way to check that your folds are actually space constant even if the value in question is a primitive, like say a byte — thunks may explode and then collapse over the run time of a single computation, defying any effort at inspection.

There are cxx and autocxx, what else do you propose to do?

I would like to see a comparison of how this compares to Rust. In terms of interoperability it has Cxx (https://cxx.rs) to offer safe bindings to C++ but also has great support for Android, Linux and many other systems. You don't even need to hack together Windows bindings (as explained in the blog post) because Microsoft offers official bindings (https://crates.io/crates/windows). I'm not sure if I'd call it a superpower if any potential interoperability has to be written to be used (compared to it already being available). Or rather, in comparison to what is interoperability a Swift superpower? Certainly not C++ or C which can be used in a far wider set of targets.

We selected Qt as a cross-platform solution. The C++/Rust interface is the clunkiest and ugliest part of the application, and rather complex because some state is shared between several windows in the GUI and several threads in the backend, and any component might modify that state at any time, and updates have to be transmitted to the other components without introducing inconsistencies. Using cxx [1] helped a little, though.

The project began in 2020, and I'm not sure what I'd choose as a GUI framework today – definitely not Qt Widgets, though.

[1] https://cxx.rs/

If the build process for the C library isn't too involved I recommend using cxx bridge (https://cxx.rs/) and letting cargo handle the build and linking. cxx basically allows you to describe the bidirectional interface (although it sounds like you only need 1 direction, which is fine too) in Rust code and it provides a "good enough" API for compiling C code inside the build.rs file.

The tooling for the first kind -- calling Rust from another language -- is a bit less developed, and tends to rely on code generation that doesn't necessarily produce a natural C API. cbindgen, uniffi, cxx, and Diplomat all take this course.

I would like to utilize OMPL's functionality in Rust code, so I want to call into OMPL C++ code somehow in Rust. I've seen two (non-mutually-exclusive) options so far: - rust-cpp, which allows you to write C++ code in Rust within the cpp!() macro. - cxx, which allows you to define both sides of the FFI boundary manually (as opposed to bindgen's automatic generation).

I'm not sure how to do this in cxx; issues like https://github.com/dtolnay/cxx/issues/447 suggest that this isn't settled yet?

I use non-vendored dependencies for the Buck build in https://github.com/dtolnay/cxx.

There's also the cpp and cxx crates for doing C++/Rust interop, but they probably aren't appropriate to use in all cases. The C ABI is definitely the safest way to go unless you're really trying to marry Rust and C++ code bases, not just writing library bindings.

There's also cxx (can't vouch for it personally but it claims to make things a lot easier) https://github.com/dtolnay/cxx