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Contents
;;; run-length-encoding.el --- run-length-encoding Exercise (exercism)
;;; Commentary:
;;; Code:
(defun run-length-group (s)
"return list of character run counts"
(let ((case-fold-search nil)
groups)
(with-temp-buffer
(insert s)
(goto-char (point-min))
(while (re-search-forward "\\(.\\)\\1*" nil t)
(push (cons
(length (match-string 0))
(match-string 1))
groups)))
(nreverse groups)))
;; (run-length-group "bbaaaac")
(defun run-length-encode (s)
"encodes a string with run-length-encoding"
(mapconcat (lambda (v)
(if (= (car v) 1)
(cdr v)
(format "%d%s" (car v) (cdr v))))
(run-length-group s)
""))
;; "2a3b4c" (run-length-encode "aabbbcccc")
(defun run-length-parse (s)
"split string into pairs containing a count and a character"
(let (rtn)
(with-temp-buffer
(insert s)
(goto-char (point-min))
(while (re-search-forward "\\([0-9]*\\)\\(.\\)" nil t)
(push (cons
(string-to-number (match-string 1))
(string-to-char (match-string 2)))
rtn)))
(nreverse rtn)))
;; (run-length-parse "2a3b4cz")
(defun run-length-decode (s)
"decodes a run-length-encoded string"
(mapconcat (lambda (n)
(make-vector (if (= (car n) 0) 1 (car n)) (cdr n)))
(run-length-parse s)
""))
(provide 'run-length-encoding)
;;; run-length-encoding.el ends here
Version data entries
24 entries across 24 versions & 1 rubygems