Converting from camelcase to _ in emacs
Use the string-inflection package, available on MELPA, or at https://github.com/akicho8/string-inflection.
Useful keyboard shortcuts, copied from https://www.emacswiki.org/emacs/CamelCase :
;; Cycle between snake case, camel case, etc.
(require 'string-inflection)
(global-set-key (kbd "C-c i") 'string-inflection-cycle)
(global-set-key (kbd "C-c C") 'string-inflection-camelcase) ;; Force to CamelCase
(global-set-key (kbd "C-c L") 'string-inflection-lower-camelcase) ;; Force to lowerCamelCase
(global-set-key (kbd "C-c J") 'string-inflection-java-style-cycle) ;; Cycle through Java styles
I use the following for toggling between camelcase and underscores:
(defun toggle-camelcase-underscores ()
"Toggle between camelcase and underscore notation for the symbol at point."
(interactive)
(save-excursion
(let* ((bounds (bounds-of-thing-at-point 'symbol))
(start (car bounds))
(end (cdr bounds))
(currently-using-underscores-p (progn (goto-char start)
(re-search-forward "_" end t))))
(if currently-using-underscores-p
(progn
(upcase-initials-region start end)
(replace-string "_" "" nil start end)
(downcase-region start (1+ start)))
(replace-regexp "\\([A-Z]\\)" "_\\1" nil (1+ start) end)
(downcase-region start (cdr (bounds-of-thing-at-point 'symbol)))))))
(progn (replace-regexp "\\([A-Z]\\)" "_\\1" nil (region-beginning) (region-end))
(downcase-region (region-beginning) (region-end)))