Emacs Lisp

Documentation

An Introduction to Programming in Emacs Lisp

C-h R eintr C-h R elisp

Emacs Lisp

M-x	desc
ielm	Emacs Lisp REPL
lisp-interaction-mode	Enable Lisp interaction mode
scratch-buffer	new scratch buffer for Emacs Lisp testing
eval-buffer	evaluate entire buffer
eval-region	evaluate marked region

Lexical binding

To enable lexical-binding in a file:

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

Keystrokes

desc	keystroke
execute line	C-x C-e
execute, dump in buffer	C-j

Limitations

From https://www.emacswiki.org/emacs/EmacsLispLimitations

EmacsLisp is a surprisingly powerful, rich dialect of Lisp. It can be used to do many things, making it practically a general use application language, and not just a language for extending Emacs.

However, you will run into certain immovable walls the further you go:

• It is not, and presumably never will be, multi-threaded.
• Once you “throw” from an inner form, you can never return to that evaluation context. In other languages, continuations allow you to do exactly that.
• There is currently no way to start a process in the background, and direct its standard output and standard error streams to different locations.
• You cannot create a n-pixel tall line of whitespace (you can, however, create an n-pixel wide character of whitespace). This becomes important if you’re trying to use graphics in Emacs 21.
• Requires launching a subprocess to read from a device file on UNIX.
• Emacs Lisp is fairly slow, and there’s not much to be done about it. Converting key algorithms to C is an arduous process which requires rebuilding Emacs.
• Memory consumption gets out-of-hand REAL FAST if you don’t pay attention. If you’re writing a new library, be sure to turn on garbage collection messages by setting ‘garbage-collection-messages’ to t. If you see the collection messages every few seconds, you can be sure that your library is eating up and spitting out cons cells and strings at a furious rate.
• Emacs cannot disown a process it has invoked. The only way is to invoke your process through “/bin/nohup” on UNIX systems. See PersistentProcesses.
• Emacs Lisp is not Scheme. See SchemeAndLisp.

Memory consumption

From https://www.emacswiki.org/emacs/EmacsLispLimitations

• Memory consumption gets out-of-hand REAL FAST if you don’t pay attention. If you’re writing a new library, be sure to turn on garbage collection messages by setting ‘garbage-collection-messages’ to t. If you see the collection messages every few seconds, you can be sure that your library is eating up and spitting out cons cells and strings at a furious rate.