Emacs lsp11/8/2023 This can also be written using the feature called advice, which allows the user to create wrappers around existing functions instead of defining their own. ) re-binds the key sequence "C-x 2" to the new function. ), defines a new function, my-split-window-func, which calls split-window-below (the old window-splitting function), then tells the new window to display another (new) buffer. ( defun my-split-window-func () ( interactive ) ( split-window-below ) ( set-window-buffer ( next-window ) ( other-buffer ))) ( global-set-key ( kbd "C-x 2" ) #' my-split-window-func ) In order to do this, the user writes the following Emacs Lisp code, in either an existing Emacs Lisp source file or an empty Emacs buffer: Suppose we wish to make it display the next available buffer. Normally, when the new window appears, it displays the same buffer as the previous one. This runs the Emacs Lisp function split-window-below. Users can press the default C-x 2 key binding to open a new window. A buffer is a region of text loaded into Emacs' memory (possibly from a file) which can be saved into a text document. In Emacs, the editing area can be split into separate areas called windows, each displaying a different buffer. Here follows a simple example of an Emacs extension written in Emacs Lisp. However, Emacs Lisp provides many features for navigating and modifying buffer text at a sentence, paragraph, or higher syntactic level as defined by modes. For example, Emacs Lisp cannot easily read a file a line at a time-the entire file must be read into an Emacs buffer. To understand the logic behind Emacs Lisp, it is important to remember that there is an emphasis on providing data structures and features specific to making a versatile text editor over implementing a general-purpose programming language. Recently, there has been an ongoing effort to update code to use lexical scoping, for reasons outlined below. That is, a function may reference local variables in the scope it is called from, but not in the scope where it was defined. A prominent characteristic of Emacs Lisp is in its use of dynamic rather than lexical scope by default. The Lisp dialect used in Emacs differs substantially from the more modern Common Lisp and Scheme dialects used for applications programming. Although the Common Lisp standard had yet to be formulated, Scheme existed at the time but Stallman chose not to use it because of its comparatively poor performance on workstations (as opposed to the minicomputers that were Emacs' traditional home), and he wanted to develop a dialect which he thought would be more easily optimized. 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. Lisp was the default extention language for Emacs derivatives such as EINE and ZWEI. It supports imperative and functional programming methods. No user interface is presented when Emacs is started in batch mode it simply executes the passed-in script and exits, displaying any output from the script.Įmacs Lisp is most closely related to Maclisp, with some later influence from Common Lisp. In this way it may be called from the command line or via an executable file, and its editing functions, such as buffers and movement commands are available to the program just as in the normal mode. When the user saves their changes, Customize simply writes the necessary Emacs Lisp code to the user's config file, which can be set to a special file that only Customize uses, to avoid the possibility of altering the user's own file.Įmacs Lisp can also function as a scripting language, much like the Unix Bourne shell or Perl, by calling Emacs in batch mode. Itself written in Emacs Lisp, Customize provides a set of preferences pages allowing the user to set options and preview their effect in the running Emacs session. Other options include the Customize feature that's been in GNU Emacs since version 20. Users of Emacs commonly write Emacs Lisp code to customize and extend Emacs. Emacs Lisp is also termed Elisp, although there are also older, unrelated Lisp dialects with that name. It is used for implementing most of the editing functionality built into Emacs, the remainder being written in C, as is the Lisp interpreter. Emacs Lisp is a dialect of the Lisp programming language used as a scripting language by Emacs (a text editor family most commonly associated with GNU Emacs and XEmacs).
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