underscore

gistfile1.el

(defun activesupport-underscore (string)
  "underscores string just like in ActiveSupport inflector"
  (let ((case-fold-search nil))
    (downcase
     (reduce (lambda (string replacement)
               (replace-regexp-in-string (car replacement) (cadr replacement) string))
             '(("::" "/")
               ("\\([[:upper:]]+\\)\\([[:upper:]][[:lower:]]\\)" "\\1_\\2")
               ("\\([[:lower:][:digit:]]\\)\\([[:upper:]]\\)" "\\1_\\2")
               ("-" "_"))
             :initial-value string))))

(defun activesupport-underscore-word ()
  "underscores word just like in ActiveSupport inflector"
  (interactive)
  (insert-string
   (activesupport-underscore
    (delete-and-extract-region (point) (+ (point) (skip-chars-forward "A-Za-z0-9:_-"))))))

Cool! Zaczynam lubic skladnie Lispowa. Kryzys wieku sredniego ;)