Comment by adamwk 19 hours ago
The subject of the function coloring article was callback APIs in Node, so an argument you need to pass to your IO functions is very much in the spirit of colored functions and has the same limitations.
The coloring is not the concrete argument (Io implementation) that is passed, but whether the function has an Io parameter in the first place. Whether the implementation of a function performs IO is in principle an implementation detail that can change in the future. A function that doesn't take an Io argument but wants to call another function that requires an Io argument can't. So you end up adding Io parameters just in case, and in turn require all callers to do the same. This is very much like function coloring.
In a language with objects or closures (which Zig doesn't have first-class support for), one flexibility benefit of the Io object approach is that you can move it to object/closure creation and keep the function/method signature free from it. Still, you have to pass it somewhere.
> Whether the implementation of a function performs IO is in principle an implementation detail that can change in the future.
I think that's where your perspective differs from Zig developers.
Performing IO, in my opinion, is categorically not an implementation detail. In the same way that heap allocation is not an implementation detail in idiomatic Zig.
I don't want to find out my math library is caching results on disk, or allocating megabytes to memoize. I want to know what functions I can use in a freestanding environment, or somewhere resource constrained.
> Performing IO, in my opinion, is categorically not an implementation detail. In the same way that heap allocation is not an implementation detail in idiomatic Zig.
It seems you two are coming at this from opposing perspectives. From the perspective of a library author, Zig makes IO an implementation detail, which is great for portability. It lets library authors freely use IO abstractions if it makes sense for their problem.
This lets you, as an application developer, decide the concrete details of how such libraries behave. Don't want your math library to cache to disk? Give it an allocating writer[0] instead of a file writer. Want to use an library with async functionality on an embedded system without multi threading? Pass it a single threaded io[1] runtime instance, implement the io interface yourself as is best for your target.
Of course someone has to decide implementation details. The choices made in designing Zig tend to focus on giving library authors useful abstractions thst give application authors meaningful control over important decisions for their application.
[0] https://ziglang.org/documentation/master/std/#std.Io.Writer....
[1] https://ziglang.org/documentation/master/std/#std.Io.Threade...
> I don't want to find out my math library is caching results on disk, or allocating megabytes to memoize. I want to know what functions I can use in a freestanding environment, or somewhere resource constrained.
On that vein, I would often like to know whether the function I can is creating a task/thread/greenlet/whatever that will continue executing, concurrently, after it returns. Making that be part of the signature is approximately called “structured concurrency”, and Zig’s design seems to conflate that with taking an io parameter. This seems a bit disappointing to me.
> A function that doesn't take an Io argument but wants to call another function that requires an Io argument can't.
Why? Can’t you just create an instance of an Io of whatever flavor you prefer and use that? Or keep one around for use repeatedly?
The whole “hide a global event loop behind language syntax” is an example of a leaky abstraction which is also restrictive. The approach here is explicit and doesn’t bind functions to hidden global state.
You can, but then you’re denying your callers control over the Io. It’s not really different with async function coloring: https://news.ycombinator.com/item?id=46126310
Scheduling of IO operations isn’t hidden global state. Or if it is, then so is thread scheduling by the OS.
Is that a problem in practice though? Zig already has this same situation with its memory allocators; you can't allocate memory unless you take a parameter. Now you'll just have to take a memory allocator AND an additional io object. Doesn't sound very ergonomic to me, but if all Zig code conforms to this scheme, in practice there will only-one-way-to-do-it. So one of the colors will never be needed, or used.
In Zig's case you pass the argument whether or not it's asynchronous, though. The caller controls the behavior, not the function being called.