小编Fra*_*ben的帖子

要么我缺少一些非常愚蠢的东西,要么特殊变量的范围对于defmethod和defun意外地不同(使用SBCL 1.1.14测试):

1. 正如所料:

   (defun ttprint-object (prefix out)
     (format out "~A: in defun: < ~A >~%" prefix *print-readably*))
   (let ((*print-readably* t))
     (format t "let: calling defun: < ~A >~%" *print-readably*)
     (ttprint-object "from let" t))
   
   let: calling defun: < T >
   from let: in defun: < T >
   

   Run Code Online (Sandbox Code Playgroud)

2. 让defmethod与defun不同,所以出乎意料:

   (defclass empty () ())
   
   (defmethod print-object ((self empty) out)
     (format out "in defmethod: < ~A >~%" *print-readably*)
     (ttprint-object "from defmethod" out))
   
   (let ((*print-readably* t))
     (ttprint-object "from let" t)
     (format t "let: calling defmethod: …

   Run Code Online (Sandbox Code Playgroud)