Concurrency. #
Cyber supports fibers as a concurrency mechanism. There are plans to support preemptive concurrency with async/await as well as multithreading.
Fibers. #
Fibers in Cyber allow representing execution contexts as first-class values. They contain their own call stack and program counters. Fibers by themselves do not enable parallelism.
The coinit creates a new fiber from a function call syntax. Using coyield inside a function pauses the current fiber and execution is returned to the fiber that invoked coresume.
count = 0
func foo():
count += 1
coyield
count += 1
fiber = coinit foo()
print count -- '0'
coresume fiber
print count -- '1'
coresume fiber
print count -- '2'
In Cyber, coyield can be used anywhere in a fiber’s call stack.
func foo():
count += 1
bar()
func bar():
-- Nested coyield in call stack.
coyield
count += 1
fiber = coinit foo()
coresume fiber
coresume also returns the resulting value. In a future version of Cyber, you will be able to yield back results and pass values back when resuming.
func foo():
return 123
fiber = coinit foo()
print(coresume fiber) -- '123'
Use Fiber.status() to get the current state of the fiber.
func foo():
coyield
print 'done'
fiber = coinit foo()
print fiber.status() -- '#paused'
coresume fiber
print fiber.status() -- '#paused'
coresume fiber
print fiber.status() -- '#done'
The main execution context is a fiber as well. Once the main fiber has finished, the VM is done and control is returned to the host.