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(librep.info)Defining Functions

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Defining Functions
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   Globally accessible functions are usually defined by the `defun'
special form.

 - Macro: defun name lambda-list body-forms...
     `defun' initialises the function definition of the symbol NAME to
     the lambda expression resulting from the concatenation of the
     symbol `lambda', LAMBDA-LIST and the BODY-FORMS.

     The BODY-FORMS may contain a documentation string for the function
     as its first form and an interactive calling specification as its
     first (if there is no doc-string) or second form if the function
     may be called interactively by the user (Note: Lambda
     Expressions).

   An example function definition taken from the `librep' source code
is:

     (defun load-all (file)
       "Try to load files called FILE (or FILE.jl, etc) from all
     directories in the Lisp load path."
       (mapc (lambda (dir)
               (let
                   ((full-name (expand-file-name file dir)))
                 (when (or (file-exists-p full-name)
                           (file-exists-p (concat full-name ".jl"))
                           (file-exists-p (concat full-name ".jlc")))
                   (load full-name nil t))))
             load-path))