RE: why not "stripes" in: (let ((zebra 'stripes) ... ; strings vs symbols?

[Drew Adams <drew.adams@oracle.com>]

> ATM i read "An Introduction to Programming in Emacs Lisp".  In
> the section where the let function is explained in detail the
> author, Robert J. Chassell, uses this "silly" example:
> 
>      (let ((zebra 'stripes)
>            (tiger 'fierce))
>        (message "One kind of animal has %s and another is %s."
>                 zebra tiger))
> 
> which when evaluated produces "One kind of animal has stripes and
> another is fierce." as output.
> 
> The thing which makes me wonder is why he uses   'stripes   instead
> of "stripes" in this example.

Either is OK.  They both produce the same effect here.
Use `C-h f format' to see what %s does (versus %S).

> In the output of the message function it makes no difference but
> to me it seems more natural to use strings here since they are
> part of a string in the output...

The beauty of %s is that you can print any Lisp object.  For a
symbol, its `symbol-name' is printed with %s.

> I do not really understand how the   'stripes   are different
> to   "stripes".  Isn't   'stripes   a notation for the symbol
> stripes?   This would mean there is the notion of a symbol which
> is bound to noting?

Yes, and yes.  Here it is irrelevant whether the symbol `stripes'
is bound to a value.

A symbol can be used for various things in Lisp.  For one thing,
It can act as a variable, having a `symbol-value'.  For another,
it can act as a function, having a `symbol-function'.

It can also act as a (rudimentary) OO object, having "slots" or
"attributes", called its symbol "properties".  These are stored
on its `symbol-plist', and are accessed using `get' and `put'.

And it need not have a non-nil value for any of these things,
in which case it at least acts as an identity, having a
`symbol-name'.

Unlike strings "stripes" and "stripes", which might be `eq' but
at least are `equal', (if in the same obarray) two symbols
`stripes and `stripes are `eq'.  They are the same Lisp object.
For one thing, that generally saves space and makes comparison
quicker.

> Could somebody please enlighten me as to what the differences
> between "stripes" and 'stripes are in which cases which notation
> is more useful/natural?

Natural is in the eye of the beholder.  But symbols are powerful
and easy to use in Lisp.  They are used a lot.