Fibers #

Pocketlang support coroutines via fibers (light weight threads with cooperative multitask). A fiber object is a wrapper around a function, contains the execution state (simply the stack and the instruction pointer) for that function, which can be run and once yielded resumed.

import Fiber

def fn(h, w)
    print(h, w)
end

fb = Fiber.new(fn)              # Create a fiber.
Fiber.run(fb, 'hello', 'world') # Run the fiber.

Yielding #

When a function is yielded, it's state will be stored in the fiber it's belongs to and will return from the function, to parent fiber it's running from (not the caller of the function). And you can pass values between fibers when they yield.

import Fiber

def fn()
    print('running')
    yield()
    print('resumed')
end

fb = Fiber.new(fn)
Fiber.run(fb)    # Prints 'running'.
print('before resumed')
Fiber.resume(fb) # Prints 'resumed'.

Yield from the fiber with a value.

import Fiber

def fn()
    print('running')
    yield(42) # Return 42.
    print('resumed')
end

fb = Fiber.new(fn)
val = Fiber.run(fb) # Prints 'running'.
print(val)          # Prints 42.
Fiber.resume(fb)    # Prints 'resumed'.

Resume the fiber with a value.

import Fiber

def fn()
    print('running')
    val = yield() # Resumed value.
    print(val)    # Prints 42.
    print('resumed')
end

fb = Fiber.new(fn)
val = Fiber.run(fb)  # Prints 'running'.
Fiber.resume(fb, 42) # Resume with 42, Prints 'resumed'.

Once a fiber is done execution, trying to resume it will cause a runtime error. To check if the fiber is finished check its attribute is_done and use the attribute function to get it's function, which could be used to create a new fiber to "re-start" the fiber.

import Fiber

Fiber.run(fb = Fiber.new(
func()
  for i in 0..5 do
    yield(i)
  end
end))

while not fb.is_done
    Fiber.resume(fb)
end

# Get the function from the fiber.
fn = fb.function