let%bind data = read_file path in
let%bind parsed = parse data in
return parsed

1let workflow path =
2    async {
3        let! data = readFile path
4        let! parsed = parse data
5        return parsed
6    }

1let workflowTask path =
2    task {
3        let! data = readFileTask path
4        let! parsed = parseTask data
5        return parsed
6    }

1let fetchAndParse url =
2    task {
3        try
4            let! raw = httpClient.GetStringAsync(url)
5            return parse raw
6        with ex ->
7            return failwithf "Fetch failed: %s" ex.Message
8    }

1let urls = [ "https://a"; "https://b"; "https://c" ]
2
3let parallelAsync =
4    urls
5|> List.map fetchAsync |> Async.Parallel let parallelTask = urls |> List.map fetchTask |> Task.WhenAll ``` Cancellation is first-class in .NET. Pass `CancellationToken` explicitly through tasks when you need cooperative cancellation across service boundaries. ## Practical Guidance for Migration If your team is mainly F# and functional-first, begin with `async {}` and add adapters where necessary: ```fsharp let taskToAsync (t: Task<'T>) = Async.AwaitTask t let asyncToTask (a: Async<'T>) = Async.StartAsTask a ``` If your dependencies are mostly modern .NET libraries, `task {}` often reduces conversion overhead and mental context switching. The key is consistency within a module to keep call chains simple. ## Practical Verification Workflow A reliable way to avoid regressions is to validate the solution in three passes: baseline, controlled change, and repeatability check. First, capture a baseline outcome before you apply fixes. This could be a failing command, a wrong output sample, a stack trace, or a screenshot of current behavior. Second, apply one focused change and rerun exactly the same checks so you can attribute improvements to a specific edit. Third, rerun the checks multiple times or with slightly different inputs to ensure the fix is not accidental or data-specific. A lightweight template you can adapt for most projects looks like this: ```bash # 1) reproduce current behavior ./run_example.sh > before.txt # 2) apply your change # edit config/code based on this article # 3) verify behavior after change ./run_example.sh > after.txt diff -u before.txt after.txt ``` If your environment involves tests, add at least one focused regression test that would fail before the fix and pass after it. This turns a one-time troubleshooting success into a durable maintenance improvement, which is especially important when teams rotate ownership or upgrade dependencies later. ## Common Pitfalls * Mixing `Async<'T>` and `Task<'T>` everywhere without a clear boundary, creating conversion noise. * Assuming OCaml Async scheduler semantics map one-to-one to .NET thread pool behavior. * Ignoring cancellation tokens in long-running operations and background services. * Treating exceptions and typed error values inconsistently across async layers. * Blocking on async (`.Result`, `.Wait()`) and causing deadlocks or thread starvation. ## Summary There is no single F# library that is a literal drop-in replacement for OCaml Async, but `async {}` and `task {}` together cover the same problem space. Use `Async<'T>` for idiomatic F# workflows, `Task<'T>` for .NET interop, and keep boundaries explicit. With consistent composition patterns and cancellation/error strategy, migration from OCaml Async concepts to F# can be smooth and maintainable.