'Required argument is not a symbol' let 绑定中的错误

Question

在下面的代码中，我得到了一个Required argument is not a symbol错误。

(defconstant +localhost+ (vector 127 0 0 1))
(defun ip-from-hostname (hostname)
(sb-bsd-sockets:host-ent-addresses
(sb-bsd-sockets:get-host-by-name hostname)))
(defun test-connect
(let ((ip (car (ip-from-hostname "www.google.com")))
(socket (make-instance 'sb-bsd-sockets:inet-socket :type :stream :protocol :tcp)))
(sb-bsd-sockets:socket-bind socket +localhost+ 8080)
(sb-bsd-sockets:socket-connect socket ip)
(sb-bsd-sockets:socket-send socket "GET / HTTP/1.1" nil)
(write-line (sb-bsd-sockets:socket-receive socket nil 2048))))
(test-connect)

更完整的错误消息：

Required argument is not a symbol: ((IP
(CAR
(IP-FROM-HOSTNAME "www.google.com")))
(SOCKET
(MAKE-INSTANCE
'SB-BSD-SOCKETS:INET-SOCKET :TYPE
:STREAM :PROTOCOL :TCP)))

我已经将问题缩小到调用ip-from-hostname的部分，但奇怪的是let绑定的简化版本在REPL:中工作

(let ((ip (sb-bsd-sockets:host-ent-addresses (sb-bsd-sockets:get-host-by-name "www.google.com"))))
(write-line (write-to-string (car ip))))

我还尝试用它的body替换ip-from-hostname调用，认为这可能与参数有关，但仍然没有成功。有什么想法吗？

Answer 1

(defun test-connect ...

...应该以缺少的lambda列表(参数列表(开头。

记住，DEFUN的语法是：

defun function-name lambda-list
[[declaration* | documentation]]
form*