filters.go
func Numbers(x, y int) Filter {
	return FilterFunc(func(arg Arg) error {
		for i := x; i <= y; i++ {
			arg.Out <- fmt.Sprint(i)
		}
		return nil
	})
}
func Numbers(x, y int) Filter {
	return FilterFunc(func(arg Arg) error {
		for i := x; i <= y; i++ {
			arg.Out <- fmt.Sprint(i)
		}
		return nil
	})
}
func Numbers ( x , y int ) Filter { return FilterFunc ( func ( arg Arg ) error { for i := x ; i <= y ; i ++ { arg . Out <- fmt . Sprint ( i ) } return nil } ) }
// Numbers emits the integers x..y
Numbers emits the integers x .. y