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Version: 0.68.0

Task Module

The Task module provides the built-in task API for concurrent execution.

Task type​

Task values use the native postfix type form:

'a task

Task.spawn : (unit -> 'a) -> 'a task​

Schedules a thunk for concurrent execution and returns an opaque task handle immediately.

let pending =
  Task.spawn (fun _ -> "done")

Notes:

  • The thunk is represented as a unit -> 'a function.
  • In script code that usually appears as fun _ -> ....
  • The returned task can be awaited later.

Task.await : 'a task -> 'a​

Waits for a task to complete and returns its result.

let pending = Task.spawn (fun _ -> 40 + 2)
let answer = Task.await pending

Runtime behavior​

  • Spawned thunks run concurrently.
  • Side effects such as print may interleave.
  • Task failures are fatal runtime errors.
  • A script cannot finish with unawaited tasks.

Example​

let left = Task.spawn (fun _ -> [1; 2; 3] |> List.map (fun n -> n * 2))
let right = [10; 20; 30] |> List.map (fun n -> n + 1)

let combined = (Task.await left) @ right
print $"{combined}"