我似乎在这里遇到了猫在盒子里的问题下面的代码应该给定一个键和一个哈希表,返回与键对应的值,或者如果键不存在于地图中则返回错误:
(defun get-graph-node (key graph)
(let ((result (gethash key graph)))
(if (nth-value 1 result)
(nth-value 0 result)
(error "no node matches the key"))))
在大多数情况下,它确实如此,但我在运行时遇到了这种奇怪的情况:
(gethash 0 *g*)
返回
#S(GRAPH-NODE$
:DATA "("$
:EDGES (#S(GRAPH-NODE :DATA "b" :EDGES NIL)$
#S(GRAPH-NODE :DATA "a" :EDGES NIL)))
T
但
(get-graph-node 0 *g*)
表示在 get-graph-node 中定义的错误
检查 *g* 给了我这个:
Count: 5
Size: 16
Test: EQL
Rehash size: 1.5
Rehash threshold: 1.0
[clear hashtable]
Contents:
0 = #S(GRAPH-NODE :DATA "(" :EDGES (#S(GRAPH-NODE :DATA "b" :EDGES NIL) #S(GRAPH-NODE :DATA "a" :EDGES NIL)))
[remove entry]
1 = #S(GRAPH-NODE :DATA "a" :EDGES NIL) [remove entry]
2 = #S(GRAPH-NODE :DATA "|" :EDGES (#S(GRAPH-NODE :DATA ")" :EDGES (NIL)))) [remove entry]
3 = #S(GRAPH-NODE :DATA "b" :EDGES NIL) [remove entry]
4 = #S(GRAPH-NODE :DATA ")" :EDGES (NIL)) [remove entry]
那么关键 0 应该在地图中吗?我向那位能告诉我我缺少什么的绅士致敬。