Automatically closing braces in emacs?

Question

Hi

I've seen a plugin for Vim called AutoClose (discovered from this post) which automatically adds the closing brace when typing '(', '{' etc.

For example; when I type the following ( | is the cursor):

int main(|

I would like the closing ) to be inserted automatically for me:

int main(|)

Does anyone know of a similar feature for emacs - Google has failed me this time!

Answer 1

yes, this mode is called electric. You can combine the electric behaviour with this simple macro for maximum confort:

(defun electric-pair ()
  "If at end of line, insert character pair without surrounding spaces.
   Otherwise, just insert the typed character."
  (interactive)
  (if (eolp) (let (parens-require-spaces) (insert-pair)) 
    (self-insert-command 1)))

Then enable it by binding the appropriate characters to it in your favorite programming modes. For example, for PythonMode:

(add-hook 'python-mode-hook
          (lambda ()
            (define-key python-mode-map "\"" 'electric-pair)
            (define-key python-mode-map "\'" 'electric-pair)
            (define-key python-mode-map "(" 'electric-pair)
            (define-key python-mode-map "[" 'electric-pair)
            (define-key python-mode-map "{" 'electric-pair)))

The CPerl mode provides this as a builtin:

;; from my .emacs
(add-hook 'cperl-mode-hook
  (lambda ()
    (setq cperl-hairy nil
   abbrev-mode t  ;; automatic keyword expansion
   cperl-highlight-variables-indiscriminately t
   cperl-auto-newline t
   cperl-auto-newline-after-colon t
   cperl-regexp-scan nil
   cperl-electric-keywords t 
   cperl-electric-linefeed t  
   cperl-electric-parens nil) ;; <------ electric parens!

Other modes could provides something similar.

Answer 2

There's also 'paredit. The cheat sheet shows you all the commands available. happen to like it better than the electric mode suggested in another answer. Though paredit does only apply to (), so it may not meed your needs.

But, to be honest, there's a bunch of packages surrounding parenthesis. The wiki has them all listed here. The modes addressing your question are:

• balancedel
• electricdotanddash
• universalcloseparen
• electricpair
• skeleton
• parenthesis
• AutoPairs

Answer 3

cmarcelo has written a wonderful post about this using skeleton mode. He also shows how to remove the balanced bracket if you delete the opening bracket and how to deal with the case that you accidentally type the closing bracket. (Incidentally both behaviors copy TextMate).

Update:

Since I posted this answer, I've discovered Autopair which is a pretty much perfect system for this use case. I've been using it a lot and loving it.