struct sensor:
    event measured: func(i32)

func (source sensor) publish(reading: i32):
    source.measured.emit(reading)

struct display:
    reading: i32

func (screen display) show(reading: i32):
    screen.reading = reading

func entry(first_reading: i32) -> i32:
    var source = sensor()
    var screen = display()
    source.measured += screen.show
    source.publish(first_reading)
    source.publish(first_reading + 1)
    return screen.reading