What are the major differences between Emacs Lisp and Common Lisp?

There's quite a bit of crossover, especially at the beginner level, so whichever you start with will mostly transfer to the other.

Some of the major differences:

  • ELisp traditionally used dynamic scoping rules; Common Lisp uses lexical scoping rules. With dynamic scoping, a function can access local variables declared in calling functions and has generally fallen out of favor. Starting with Emacs 24, Emacs allows optional lexical scoping on a file-by-file basis (and all files in the core distribution are progressively being converted).

  • Dynamically scoped ELisp doesn't have closures, which makes composing functions and currying difficult. There's a apply-partially function that works similarly to currying. Note that the lexical-let form introduced in Emacs 24 makes it possible to produce closures via lexical scoping.

  • Much of the Common Lisp library that has been built up over time isn't available in elisp. A subset is provided by the elisp cl package

  • elisp doesn't do tail-call optimization.


These Emacs-Wiki pages offer some info about the relation between the two Lisps and their differences:

  • http://www.emacswiki.org/emacs/CommonLisp
  • http://www.emacswiki.org/emacs/EmacsLisp
  • http://www.emacswiki.org/emacs/EmacsLispLimitations