修正练习 2.56 答案中的 bug ，感谢 James Liang 的提醒：

http://sicp.readthedocs.org/en/latest/chp2/56.html#comment-683927422
go-to-win · Oct 16, 2012 · c234c67 · c234c67
1 parent 3342b06
commit c234c67
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diff --git a/chp2/code/56-deriv.scm b/chp2/code/56-deriv.scm
@@ -33,7 +33,7 @@
 
 (define (make-exponentiation base exponent)                         ; 新增
     (cond ((= exponent 0)                                           ;
-            0)                                                      ;
+            1)                                                      ;
           ((= exponent 1)                                           ;
             base)                                                   ;
           (else                                                     ;

diff --git a/chp2/code/test-56-deriv.scm b/chp2/code/test-56-deriv.scm
@@ -7,7 +7,7 @@
             0)
 
     (equal? (deriv '(** x 1) 'x)
-            0)
+            1)
 
     (equal? (deriv '(** x 2) 'x)
             '(* 2 x))
-Original file line number
+Diff line change
@@ Expand Up / @@ -33,7 +33,7 @@ @@
     (define (make-exponentiation base exponent)                         ; 新增
         (cond ((= exponent 0)                                           ;
-)                                                      ;
+)                                                      ;
               ((= exponent 1)                                           ;
                 base)                                                   ;
               (else                                                     ;
@@ Expand Down @@