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The [LISP]-based scripting language used to customise the [Emacs] programmers' editor.

Emacs is completely scriptable in Elisp - look in /usr/share/emacs/site-lisp/*.el for the start-up and config files.

''[Programming in Emacs Lisp | http://www.delorie.com/gnu/docs/emacs-lisp-intro/emacs-lisp-intro.html]'' is an online book about Emacs scripting by Robert J. Chassell. It does not assume you already know Lisp.

!!! Note for Lisp programmers
ELisp is __dynamically scoped__. This affects how global variables in function definitions are looked up. With dynamic scoping the interpreter looks up these variables in the environment where the function is ''called''.  What other [LISP] do is to use the variable definitions that were present when the function was ''defined'' (i.e. ''lexical scoping''). This difference will only effect you if you are trying to do lots of [higher-order functional programming | HigherOrderFunctions] in ELisp, but if you do, it will trip you up.

!!!Example

This sets up the F12 key to instantly save and close a file that Emacs is editing:

 (defun begins-with-p (str sub)
   "True if string `str' begins with substring `sub'."
   (and (>= (length str) (length sub))
        (string= (substring str 0 (length sub)) sub)))

 (defun put-away-buffer (&optional buffer)
   "This kills a buffer, saving its contents first, if necessary.
     Internal and *scratch* buffers are ignored."
   (interactive)
   (unless buffer
     (setq buffer (current-buffer)))
   (unless (or (begins-with-p (buffer-name buffer) " ")  ;ignore internal buffers
               (string= "*scratch*" (buffer-name buffer)))  ;ignore scratch buffer
     (when (and (buffer-file-name buffer) ;is visiting a file
                (buffer-modified-p buffer))
       (save-buffer))
     (kill-this-buffer)))

 (global-set-key [[f12]  #'put-away-buffer)

----
CategoryProgrammingLanguages, CategoryFunctionalProgrammingLanguages

4 pages link to Elisp:

Last edited on Wednesday, November 19, 2003 4:16:32 pm by AristotlePagaltzis

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