查找 Common Lisp 中的字符频率

Question

例如，如果我输入字符序列

“你好世界” H = 1 e = 1 l = 3 o - 2 r = 1 w = 1 d = 1

有人能帮我吗

我在网上找到了这段代码，但我不明白它，我想要一个更简单的代码

(defun letter-freq (file)
 (with-open-file (stream file)
  (let ((str (make-string (file-length stream)))
        (arr (make-array 256 :element-type 'integer :initial-element 0)))
    (read-sequence str stream)
    (loop for c across str do (incf (aref arr (char-code c))))
    (loop for c from 32 to 126 for i from 1 do
      (format t "~c: ~d~a"
        (code-char c) (aref arr c)
        (if (zerop (rem i 8)) #\newline #\tab))))))

(letter-freq "test.lisp")

Answer 1

上面的代码是针对 ASCII 字符的。如果您想对任何可能的字符执行相同的操作，可以使用哈希表。

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(defun letter-freq (file)\n  (with-open-file (stream file)\n    (let ((str (make-string (file-length stream)))\n          (ht (make-hash-table)))\n      (read-sequence str stream)\n      (loop :for char :across str :do\n        (incf (gethash char ht 0)))\n      (maphash (lambda (k v)\n                 (format t "~@C: ~D~%" k v))\n               ht))))\n

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~@Cformat 指令打印chara\xd1\x81ter，就像通过prin1.

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