lisp 變數的作用域

lisp  的變數 作用域是 lexical scoping 的


我們看看下面的程式碼：

CL-USER> (setf c 'global-c)

; in: SETF C
;     (SETF C 'GLOBAL-C)
; ==>
;   (SETQ C 'GLOBAL-C)
;
; caught WARNING:
;   undefined variable: C
;
; compilation unit finished
;   Undefined variable:
;     C
;   caught 1 WARNING condition
GLOBAL-C
CL-USER> (defvar *d* 'global-d)
*D*
CL-USER> (defun fn() *b*)
STYLE-WARNING: redefining COMMON-LISP-USER::FN in DEFUN
FN
CL-USER> fn
; Evaluation aborted on #.
CL-USER> (fn
      )
GLOBAL-B
CL-USER> (let (( c 'local-c)
           (*d* 'local-d))
       (list c *d* (fn) (symbol-value 'c) (symbol-value '*d*)))
(LOCAL-C LOCAL-D GLOBAL-B GLOBAL-C LOCAL-D)
CL-USER>

看結果不解釋