Synonym for Stdlib.Lazy.Undefined.

Represents a deferred computation or suspension.

from_fun thunk returns a suspension.

from_val value returns an already forced suspension whose result is the given value.

is_val susp determines whether the suspension has already been forced and didn't raise an exception.

force susp forces the suspension, i.e. computes thunk () using the thunk passed to from_fun, stores the result of the computation to the suspension and reproduces its result. In case the suspension has already been forced the computation is skipped and stored result is reproduced.

ℹ️ This will check whether the current fiber has been canceled before starting the computation of thunk (). This allows the suspension to be forced by another fiber. However, if the fiber is canceled and the cancelation exception is raised after the computation has been started, the suspension will then store the cancelation exception.

• raises Undefined

  in case the suspension is currently being forced by the current fiber.

force_val is a synonym for force.

map fn susp is equivalent to from_fun (fun () -> fn (force susp)).

map_val fn susp is equivalent to:

  if is_val susp then
    from_val (fn (force susp))
  else
    map fn susp