在Common Lisp中@表示什么？

Question

我遇到了以下代码片段:

(defstructure object
  "An object is anything that occupies space.  Some objects are 'alive'."
  (name "?")            ; Used to print the object on the map
  (alive? nil)                  ; Is the object alive?
  (loc (@ 1 1))         ; The square that the object is in
  (bump nil)            ; Has the object bumped into something?
  (size 0.5)            ; Size of object as proportion of loc
  (color 'black)        ; Some objects have a color
  (shape 'rectangle)        ; Some objects have a shape
  (sound nil)           ; Some objects create a sound
  (contents '())        ; Some objects contain others
  (max-contents 0.4)            ; How much (total size) can fit inside?
  (container nil)       ; Some objects are contained by another
  (heading (@ 1 0))     ; Direction object is facing as unit vector
  )

我不确定这里的@是什么意思.我已经搜索了其余的代码,看看它是否被定义为一个函数,但却找不到任何东西.我的问题,是"@"常用lisp的一些常用实现的一部分,还是这个代码具体？谢谢.

链接到文件:https: //github.com/aimacode/aima-lisp/blob/master/agents/environments/grid-env.lisp

Answer 1

该功能定义utilities/utilities.lisp如下:

(defun @ (x y) "Create a 2-D point" (make-xy :x x :y y))

它创建一个点(或矢量).

为了找到定义,我不得不克隆存储库,因为GitHub搜索在搜索代码时几乎没用:

find -name "*.lisp" -exec grep -H @ {} \; 

...
./utilities/utilities.lisp:(defun @ (x y) "Create a 2-D point" (make-xy :x x :y y))
...

我没有搜索,defun因为它也可能是一个宏.