RosettaCodeData/Task/Queue-Definition/V-(Vlang)/queue-definition.v

const max_tail = 256

struct Queue[T] {
	mut:
	data  []T
	tail  int
	head  int
}

fn (mut queue Queue[T]) push(value T) {
	if queue.tail >= max_tail || queue.tail < queue.head { return }
	println("Enqueue: $value")
	queue.data << value
	queue.tail++
}

fn (mut queue Queue[T]) pop() !T {
	if queue.tail > 0 && queue.head < queue.tail {
		result := queue.data[queue.head]
		queue.head++
		println("Dequeue: top of Queue was $result")
		return result
	}
	return error("Queue Underflow!!")
}

fn (queue Queue[T]) peek() !T {
	if queue.tail > 0 && queue.head < queue.tail {
		result := queue.data[queue.head]
		println("Peek: top of Queue is $result")
		return result
	}
	return error("Out of Bounds...")
}

fn (queue Queue[T]) empty() bool {
	return queue.tail == 0
}

fn main() {
	mut queue := Queue[f64]{}
	println("Queue is empty? " + if queue.empty() { "Yes" } else { "No" })
	queue.push(5.0)
	queue.push(4.2)
	println("Queue is empty? " + if queue.empty() { "Yes" } else { "No" })
	queue.peek() or { return }
	queue.pop() or { return }
	queue.pop() or { return }
	queue.push(1.2)
}