Emacs regexp计数发生

Question

我正在寻找最快的例程(不是交互式)来获取字符串中正则表达式的匹配数.

就像是

(count-occurrences "a" "alabama")
=> 4

Answer 1

count-matches是否以交互方式进行.也许是一个开始寻找的好地方.

Answer 2

how-many(别名count-matches)这样做,但适用于缓冲区.

这是一个适用于字符串:

(defun how-many-str (regexp str)
  (loop with start = 0
        for count from 0
        while (string-match regexp str start)
        do (setq start (match-end 0))
        finally return count))

Answer 3

这是一个使用递归和累加器的更实用的答案.作为额外的好处,它不使用cl:

(defun count-occurences (regex string)
  (recursive-count regex string 0))

(defun recursive-count (regex string start)
  (if (string-match regex string start)
      (+ 1 (recursive-count regex string (match-end 0)))
    0))