寻找在2D Lisp数组上映射函数的方法

• dotimes
• array-dimensions
• make-array
• array-total-size
• row-major-aref

(defun array-map (function array
                  &optional (retval (make-array (array-dimensions array))))
  "Apply FUNCTION to each element of ARRAY.
Return a new array, or write into the optional 3rd argument."
  (dotimes (i (array-total-size array) retval)
    (setf (row-major-aref retval i)
          (funcall function (row-major-aref array i)))))

例子:

(defparameter a (make-array '(2 3) :initial-contents '((1 2 3) (4 5 6))))
a
==> #2A((1 2 3) (4 5 6))
(array-map #'sqrt a)
==> #2A((1 1.4142135 1.7320508) (2 2.236068 2.4494898))
a ; does not change!
==> #2A((1 2 3) (4 5 6))

array-map 类似 map-into

(array-map #'1+ a a)
==> #2A((2 3 4) (5 6 7))
a   ; modified, no new storage is allocated
==> #2A((2 3 4) (5 6 7))

那个 阵列映射 将适用于任何数组维度,从向量到矩阵,再到10d&c

运动 array-multi-map 接受任意数量的参数和任意数量的数组的函数,以便

(array-multi-map #'+ #A((1 2 3) (4 5 6)) #A((11 22 33) (44 55 66)))
==> #A((12 24 36) (48 60 72))

附言 .整体 CLHS Chapter 15 Arrays CLtL2 Chapter 17 Arrays