Emacs Lisp

Emacs Lisp
Library	lisp-mode
Command	emacs-lisp-mode
Builtin	yes
Auto-activates for	*.el, .emacs, _emacs

Emacs Lisp is a dialect of the Lisp programming language used by GNU Emacs. Most of the editing functionality built into Emacs is written in Emacs Lisp, with the remainder being written in C (as is the Lisp interpreter itself). Users of Emacs commonly write Emacs Lisp code to customize and extend Emacs.

Emacs Lisp is also commonly referred to as "elisp" or "Elisp". Files containing Emacs Lisp code use the .el filename suffix; when byte-compiled, the same filename prefix is used but with the .elc filename suffix.

Emacs Lisp is a Lisp-2, which means that a single identifier (in Lisp terminology, "symbol") can simultaneously exist as ("be bound to") both a function and a variable.

Basic setup

You can customize the way Emacs edits and displays this and all other lisp languages with M-x customize-group RET lisp RET.

Helpful keybindings

[M-TAB]: Complete at point

[C-M-q]: Indent the S-expression following point

[C-M-x]: Evaluate the defun at point

Common customizations

Outlining

For Org-style outlining, add the following snippet to your Emacs configuration file.

;; Turn on outline minor mode
(add-hook 'emacs-lisp-mode-hook  'outline-minor-mode)

;; Add key bindings for Org-style outline cycling
(add-hook 'outline-minor-mode-hook
  (lambda ()
    (define-key outline-minor-mode-map [(control tab)] 'org-cycle)
    (define-key outline-minor-mode-map [(shift tab)] 'org-global-cycle)))

Now visit any elisp file (say M-x find-library RET outline) and keep pressing [S-TAB] and see what happens. Experiment similarly with [C-TAB].

Indentation

Add the following snippet to your Emacs configuration file, so that you don't have to indent deliberately. See M-x reindent-then-newline-and-indent.

(add-hook 'emacs-lisp-mode-hook
	  (lambda nil
	    (local-set-key [(return)] 'reindent-then-newline-and-indent)))

Always keep parentheses balanced

See Skeleton#Keep some chars always balanced

Scope

By default elisp uses dynamic scope. Since Emacs 24 lexical scope has been added.
To use lexical binding, an Emacs-lisp source file must set a file-variable lexical-binding to t in the file header, e.g., by using a first line like:

   ;;; -*- lexical-binding: t -*-

External links

Emacs Lisp manual
Programming in elisp, libreplanet.org wiki
EmacsLips, from emacswiki.org