编译 Common Lisp 代码时出现奇怪的错误

Question

我在尝试编译一些代码时遇到以下错误：

Lambda list of method # is incompatible with that of the generic function INITIALIZE-INSTANCE. Method's lambda-list : (PAT::E) Generic-function's : (CCL::INSTANCE &REST CCL::INITARGS &KEY &ALLOW-OTHER-KEYS)

这是导致错误的代码：

(defclass event ()
  ((timestamp
    :initarg :timestamp
    :accessor timestamp)
   (value
    :initarg :value
    :accessor value)))

(defclass update (event)
  ((security
    :initarg :sectype
    :accessor sectype)))

(defclass prc (update)
  ((lastp
    :accessor lastp)
   (lastv
    :accessor lastv)))

(defmethod initialize-instance :after ((e prc)) ; <- :(
  (setf (lastp e) (first (value e)))
  (when (second (value e))
    (setf (lastv e) (second (value e)))))

任何关于可能导致错误的提示都将不胜感激。

Answer 1

您需要在 initialize-instance 方法的参数列表末尾添加 &key。

引用自 "Practical Common Lisp"，章节“17. 对象重定向：类”：

The &key in the parameter list is required to keep the method's parameter list congruent with the generic function's--the parameter list specified for the INITIALIZE-INSTANCE generic function includes &key in order to allow individual methods to supply their own keyword parameters but doesn't require any particular ones. Thus, every method must specify &key even if it doesn't specify any &key parameters.

编译 Common Lisp 代码时出现奇怪的错误

Weird error when compiling Common Lisp code

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