Re: quote doesn't produce a fresh object

[Kevin Rodgers]

Don Bashford wrote:
> (defun myfun (x)
>   (let ((xs '(nil)))
>     (print xs)
>     (setcar xs "foo"))
>   t)
>
> On first invocation, (myfun 'arg) prints (nil) and returns t, as
> expected.  But on second invocation, it prints ("foo").  It seems in the
> second invocation, the let variable xs gets the old object from the
> previous invocation.  If '(nil) is changed to (list nil) in myfun, the
> problem does not occur, so the problem is with quote, not with let.

That is not a bug. 'FORM is equivalent to (quote FORM) and is used to
denote a constant Lisp object, so the xs symbol should reference the
original object (which is cons'ed when the defun form is read, not when
it is evaluated).

--
Kevin Rodgers