Re: A couple rudimentary elisp questions

[exits funnel <exitsfunnel@yahoo.com>]

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> In emacs lisp there's no multiline comment. You can
> use
> comment-region / uncomment-region to comment several
> lines at once.
> 
> Otherwise you can use this trick: use a multi-line
> string as a
> comment, like you do for documentation strings:
> 
> (defun my-fun ()
>     " This
> is the documentation
> string of the function
> my-fun that appears 
> when you ask for the 
> function documentation
> with (describe-function 'my-fun)
> or C-h C-f my-fun RET
> "
>     (do-something)
>     " Here is a ''comment''
>       spread on several
>       lines.
>       Actually, it's not a 
>       comment, it's a string
>       that is ''evaluated''
>       in the course of this
>       function, but since
>       we don't do anything
>       with it, it's finally
>       ignored. "
>     (do-something-else)
>     (get-result))
> 
> Of course, since the strings are syntactically
> significant, you must
> take care where you put them. You can't put them
> inside function
> argument lists, or inside other data lists.  They
> eventually get
> ignored only in statement lists, inside progn and
> equivalent (and not
> in a result position!).
> 
> Perhaps a cleaner way to do it would be to defined a
> comment macro:
> 
>     (defmacro rem (&rest args))
> 
>     (defun my-fun ()
>     " This
> is the documentation
> string of the function
> my-fun that appears 
> when you ask for the 
> function documentation
> with (describe-function 'my-fun)
> or C-h C-f my-fun RET
> "
>     (do-something)
>     (rem Here we have a "comment"
>          but it is still scanned
>          and tokenized.
>          "So we may still use strings
>           and use any kind of invalid
>           token such as . . . :-)
>           But note that you must still
>           escape double-quotes such as: \"
>         ")
>     (do-something-else)
>     (get-result))
> 
> You get two advantages with this rem macro:
> 
>     1- a code walker can find your comments if you
> need to process them.
> 
>     2- since the macro generates nothing, the
> comment/strings don't
>        eventually appear in compiled code, and the
> execution  of
>        compiled code is strictly equivalent with or
> without the (rem ...)
>        (that could be not the case without the
> macro).


> It's the notation for a cons cell:
> 
>     (cons 'foo 'bar) == (foo . bar)
> 
> Lists are built on cons cells, starting from the
> empty list ():
> 
>     (cons 'foo ())             == (foo . ())        
>  == (foo)
> 
>     (cons 'bar (cons 'foo ())) == (bar . (foo . ()))
>  == (bar foo)
> 
>     (cons 'baz
>       (cons 'bar
>          (cons 'foo ()))) == (baz . (bar . (foo .
> ()))) == (baz bar foo)
> 
> 
> The value assigned to the symbol nil is (), the
> empty list, which is
> actually a special atom. 
> The empty list () is NOT a cons: (consp ()) == nil,
> (atom ()) == t.

Pascal, I just wanted to take a quick moment to thank
you for your detailed reply.  All of the information
was very helpful.  

-exits

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