普通 LISP 中的嵌套循环

Question

我正在尝试创建一个可以在 LISP 中解决游戏 Mastermind 的玩家。我尝试在辅助函数中使用以下嵌套循环

(defparameter *counter* 0) 

;analyze the score to determine whether points need to be added to counter
(defun analyze (last-response)
  (if (> (first last-response) 0)
      (setf *counter* (+ (first last-response) *counter*))))

;helper function for finding correct color
(defun guessColor (length colors last-response)
    (loop while (< *counter* 4) do
       (loop for i from 1 to length
          collect (first colors)
          (setf colors (rest colors)))
    (analyze (last-reponse))))

;baseline Holyguacamole player will guess all colors before trying all combinations of correct color 
(defun HolyGuacamole (board colors SCSA last-response)
  (declare (ignore SCSA))
  ;(print last-response)
  (guessColor board colors last-response)
  (print *counter*)
    ;(sortColor)
)

while 循环应该在全局变量*counter* 小于 4 时运行。内部循环应该根据所需的钉子长度（可变长度）猜测颜色。我一直遇到编译错误

在 (LOOP WHILE (COUNTER 4) ...) 的宏展开期间。使用 ;
BREAK-ON-SIGNALS 拦截。

我不熟悉 LISP，所以我不确定该错误代码的含义以及如何修复它。我觉得我用正确的括号正确地嵌套了它，但我实际上不确定它有什么问题。

Link 到 Mastermind 环境。

Answer 1

原则上，将一个循环嵌套在另一个循环中是没有障碍的。但是，@jkiiski 指出，COLLECT 或 COLLECTING 子句只能采用单个表达式。

比如下面这个程序

(defun nested-loop ()
  (loop for i from 1 to 10 doing
        (loop for j from 1 to 10 collecting
              (print "some string")
              (print (list 'nested-loop i j)))))

(nested-loop)

在 CLISP 下产生语法错误。

*** - LOOP: illegal syntax near (PRINT (LIST 'NESTED-LOOP I J)) in
       (LOOP FOR J FROM 1 TO 10 COLLECTING (PRINT "some string")
        (PRINT (LIST 'NESTED-LOOP I J)))

使用do 或doing 子句有效，将与collecting 子句关联的多个表达式与progn 分组也是如此。

(defun nested-loop ()
  (loop for i from 1 to 10 doing
        (loop for j from 1 to 10 collecting
              (progn
                (print "some string")
                (print (list 'nested-loop i j))))))

(nested-loop)