for u = range 256 {
}

// invalid: 1e3 is a floating-point constant
for range 1e3 {
}

// fibo generates the Fibonacci sequence
fibo := func(yield func(x int) bool) {
	f0, f1 := 0, 1
	for yield(f0) {
		f0, f1 = f1, f0+f1
	}
}

// print the Fibonacci numbers below 1000:
for x := range fibo {
	if x >= 1000 {
		break
	}
	fmt.Printf("%d ", x)
}