14. Workers

let work = spawn render(scene)
let other = spawn render(other_scene)
let (a, b) = (wait work, wait other)

spawn f(args) starts f on another worker with copies of its arguments and yields a task[T]; wait task yields its result, or its failure if f is !. Arguments and results are sendable: scalars, str, bytes, tuples, structs and enums of sendable members, optionals and results of them, and copies of collections of them. A class instance, a closure, or a collection identity never crosses. f is a named function of the program, never a method, a closure or a Base function. A task is bound and waited, once, by the function that spawned it: it is not stored in a field or a collection, returned, or captured. A worker's tasks are waited before the function that spawned them returns; a failure or a return cancels the rest, whose results are discarded when they end. Workers share nothing, so there are no locks and no races in the language; what a worker prints interleaves with other output in an order the program does not fix, and the interpreter runs each task when it is spawned.