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(texinfo)Sample Function Definition

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A Sample Function Definition
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  A function definition uses the `@defun' and `@end defun' commands.
The name of the function follows immediately after the `@defun' command
and it is followed, on the same line, by the parameter list.

  Here is a definition from Note: Calling Functions.


      - Function: apply function &rest arguments
          `apply' calls FUNCTION with ARGUMENTS, just like `funcall'
          but with one difference: the last of ARGUMENTS is a list of
          arguments to give to FUNCTION, rather than a single argument.
          We also say that this list is "appended" to the other
          arguments.

          `apply' returns the result of calling FUNCTION.  As with
          `funcall', FUNCTION must either be a Lisp function or a
          primitive function; special forms and macros do not make
          sense in `apply'.

               (setq f 'list)
                    => list
               (apply f 'x 'y 'z)
               error--> Wrong type argument: listp, z
               (apply '+ 1 2 '(3 4))
                    => 10
               (apply '+ '(1 2 3 4))
                    => 10
               
               (apply 'append '((a b c) nil (x y z) nil))
                    => (a b c x y z)

          An interesting example of using `apply' is found in the
          description of `mapcar'.

  In the Texinfo source file, this example looks like this:

     @defun apply function &rest arguments
     @code{apply} calls @var{function} with
     @var{arguments}, just like @code{funcall} but with one
     difference: the last of @var{arguments} is a list of
     arguments to give to @var{function}, rather than a single
     argument.  We also say that this list is @dfn{appended}
     to the other arguments.
     
     @code{apply} returns the result of calling
     @var{function}.  As with @code{funcall},
     @var{function} must either be a Lisp function or a
     primitive function; special forms and macros do not make
     sense in @code{apply}.
     
     @example
     (setq f 'list)
          @result{} list
     (apply f 'x 'y 'z)
     @error{} Wrong type argument: listp, z
     (apply '+ 1 2 '(3 4))
          @result{} 10
     (apply '+ '(1 2 3 4))
          @result{} 10
     
     (apply 'append '((a b c) nil (x y z) nil))
          @result{} (a b c x y z)
     @end example
     
     An interesting example of using @code{apply} is found
     in the description of @code{mapcar}.
     @end defun

In this manual, this function is listed in the Command and Variable
Index under `apply'.

  Ordinary variables and user options are described using a format like
that for functions except that variables do not take arguments.