Zig's new plan for asynchronous programs

The three most prevalent themes in the discussion revolving around Zig's I/O abstraction and "function coloring" are:

1. The Debate Over Explicit I/O Parameters as "Function Coloring": There is a significant disagreement on whether requiring an explicit Io parameter for functions that perform I/O constitutes the undesirable "function coloring" problem seen in traditional async/await scenarios.

   • One side argues that forcing the Io parameter onto functions that need it effectively colors functions (IO vs. non-IO), leading to boilerplate and separation issues, similar to sync vs. async separation. As user unscaled noted, by the original definition, Zig's approach follows the points: "Red functions require an Io argument. Blue functions do not."
   • The opposing view is that coloring only truly occurs when the calling syntax differs (e.g., await vs. direct call), which is avoided in Zig since synchronous and asynchronous I/O are called the same way (by passing the io parameter). User mk12 stated this distinction clearly: "Colors for 2 ways of doing IO vs colors for doing IO or not are so different that it’s confusing to call both of them “function coloring problem”. Only the former leads to having to duplicate everything (sync version and async version)."

2. Ergonomics vs. Flexibility in Concurrency Models: Users weighed the immediate convenience of syntactic tools like async/await against the long-term flexibility offered by Zig's explicit dependency injection of the I/O environment.

   • Proponents of traditional colored concurrency argue for ergonomics: User giancarlostoro noted that async/await in languages like C# and Python "drastically went away" the mental overhead.
   • Advocates for Zig's approach emphasize flexibility and portability, making library code agnostic to the underlying runtime (sync vs. async, threaded vs. evented). User messe argued for this utility: "It's valuable to library authors who can now write code that's agnostic of the users' choice of runtime, while still being able to express that asynchronicity is possible for certain code paths."

3. Comparison to Managed Language Concurrency (Go, Java, C#): The discussion frequently benchmarked Zig's explicit I/O against languages that implicitly manage concurrency or I/O context via language features or runtime structures (goroutines, virtual threads, async keywords).

   • Several users expressed preference for these implicit models. User osigurdson was glad Zig avoided keywords, stating: "Glad Zig took this 'colorless' approach."
   • However, deep differences were highlighted, particularly regarding Go channels versus futures, and the implementation cost of implicit models. User jerf elaborated on the subtle but critical difference between Go channels and basic thread-safe queues, noting that Go's features are "fairly heavyweight as concurrency operations go" because they implement more functionality than a simple queue.