lisp-猜数字算法与全局函数、变量

* (defvar *big* 100)  
  
*BIG*  
* (defvar *small* 1)  
*SMALL*  
  
   
  
50  
0] (defun smaller() (setf *big* (1- (guess-number)))(guess-number))  
  
SMALLER  
0] (defun bigger() (setf *small* (1+ (guess-number)))(guess-number))  
  
* (defun guess-number() (ash (+ *small* *big*) -1))  
STYLE-WARNING: redefining COMMON-LISP-USER::GUESS-NUMBER in DEFUN  
  
GUESS-NUMBER  
* guess-number  
  
0[2] (smaller)  
; No debug variables for current frame: using EVAL instead of EVAL-IN-FRAME.  
25  
0[2] (bigger)  
; No debug variables for current frame: using EVAL instead of EVAL-IN-FRAME.  
37  
0[2] (bigger)  
; No debug variables for current frame: using EVAL instead of EVAL-IN-FRAME.  
43  
0[2] (smaller)  
; No debug variables for current frame: using EVAL instead of EVAL-IN-FRAME.  
40  
0[2] (smaller)  
; No debug variables for current frame: using EVAL instead of EVAL-IN-FRAME.  
38 

我们设定数字是38

defvar定义全局变量,defparameter也是，但是defparameter语句可以反复使用，多次定义一个变量或改变量的值

比如

(defparameter xx 100)

然后再执行一次

(defparameter xx 101)

那么此时

xx是101

而

defvar则不同

(defvar xx 100)

然后再执行一次

(defvar xx 101)

那么此时

xx是100