编写程序，实现队列的基本运算：入队、出队、输出队、取队头、取队尾、求队长、清空队，要求采用顺序循环队实现。

以下是基于Python语言实现的顺序循环队列：

class Queue:
    def __init__(self, size):
        self.size = size  # 队列长度
        self.queue = [0] * size  # 初始化队列
        self.head = 0  # 队首指针
        self.tail = 0  # 队尾指针
        self.length = 0  # 队列长度

    def enqueue(self, value):
        """入队操作"""
        if self.length == self.size:
            print("队列已满，无法入队")
            return False
        self.queue[self.tail] = value
        self.tail = (self.tail + 1) % self.size
        self.length += 1
        return True

    def dequeue(self):
        """出队操作"""
        if self.length == 0:
            print("队列为空，无法出队")
            return None
        value = self.queue[self.head]
        self.head = (self.head + 1) % self.size
        self.length -= 1
        return value

    def output(self):
        """输出队列"""
        if self.length == 0:
            print("队列为空")
            return
        print("队列元素为：", end="")
        i = self.head
        while i != self.tail:
            print(self.queue[i], end=" ")
            i = (i + 1) % self.size
        print()

    def get_head(self):
        """取队头元素"""
        if self.length == 0:
            print("队列为空")
            return None
        return self.queue[self.head]

    def get_tail(self):
        """取队尾元素"""
        if self.length == 0:
            print("队列为空")
            return None
        return self.queue[(self.tail - 1) % self.size]

    def length(self):
        """求队列长度"""
        return self.length

    def clear(self):
        """清空队列"""
        self.head = 0
        self.tail = 0
        self.length = 0
        print("队列已清空")

使用示例：

q = Queue(5)
q.enqueue(1)
q.enqueue(2)
q.enqueue(3)
q.output()  # 队列元素为：1 2 3
q.dequeue()
q.output()  # 队列元素为：2 3
print(q.get_head())  # 2
print(q.get_tail())  # 3
print(q.length)  # 2
q.clear()
q.output()  # 队列为空