Editing Emacs Lisp (section)

==Compared to other Lisp dialects==
Emacs Lisp is most closely related to [[Maclisp]], with some later influence from [[Common Lisp]].<ref>"GNU Emacs Lisp is largely inspired by [[Maclisp]], and a little by Common Lisp.  If you know Common Lisp, you will notice many similarities. However, many features of Common Lisp have been omitted or simplified in order to reduce the memory requirements of GNU Emacs.  Sometimes the simplifications are so drastic that a Common Lisp user might be very confused.  We will occasionally point out how GNU Emacs Lisp differs from Common Lisp." – from the "History" section of the "Introduction" to the Emacs Lisp Manual, as of Emacs 21</ref> It supports [[procedural programming|imperative]] and [[functional programming]] methods. Lisp was the default extension language for Emacs derivatives such as [[EINE and ZWEI]]. When [[Richard Stallman]] forked [[Gosling Emacs]] into GNU Emacs, he also chose Lisp as the extension language, because of its powerful features, including the ability to treat functions as data. Although the Common Lisp standard had yet to be formulated, [[Scheme (programming language)|Scheme]] existed at the time but Stallman chose not to use it because of its comparatively poor performance on workstations (as opposed to the [[minicomputer]]s that were Emacs' traditional home), and he wanted to develop a dialect which he thought would be more easily optimized.<ref>"So the development of that operating system, the GNU operating system, is what led me to write the GNU Emacs. In doing this, I aimed to make the absolute minimal possible Lisp implementation. The size of the programs was a tremendous concern. There were people in those days, in 1985, who had one-megabyte machines without virtual memory. They wanted to be able to use GNU Emacs. This meant I had to keep the program as small as possible." – from [https://www.gnu.org/gnu/rms-lisp.html "My Lisp Experiences and the Development of GNU Emacs"]</ref>

The Lisp dialect used in Emacs differs substantially from the more modern Common Lisp and Scheme dialects used for applications programming. A prominent characteristic of Emacs Lisp is in its use of dynamic rather than lexical [[scope (computer science)|scope]] by default. That is, a function may reference local variables in the scope it is called from, but not in the scope where it was defined. Recently, there has been an ongoing effort to update code to use lexical scoping, for reasons outlined below.

{{Lisp}}