Sync Method calls

While async is good for performance it makes it somewhat convoluted, forcing use of callbacks, to just return a value. Acton makes it possible to call other actors in a synchronous fashion for ease of use.

A method is called synchronously when the return value is used.

Source:

import acton.rts

actor DeepT():
    def compute():
        # some heavy computation going on
        acton.rts.sleep(1)
        return 42

actor main(env):
    d1 = DeepT()

    answer = d1.compute()
    print("The answer is", answer)

    env.exit(0)

Compile and run:

actonc sync.act

Output:

The answer is 42

The call flow can be illustrated like this. We can see how the execution of main is suspended while it is waiting for the return value from actor d1.

While synchronous is bad because we block waiting for someone else, we are only ever going to wait for another actor to run its method. There is never any wait for I/O or other indefinite waiting, only blocking wait for computation within the Acton system. This is achieved by the lack of blocking calls for I/O, thus even if there is a chain of actors waiting for each other