Re: A small backquote logjam

[bolega]

On Jun 10, 6:29 pm, Barry Margolin <bar...@alum.mit.edu> wrote:
> In article
> <a50f19e2-b95f-4bc4-b389-aa5dff67f...@x21g2000yqa.googlegroups.com>,
>
>  bolega <gnuist...@gmail.com> wrote:
> > (progn (setq y '(a b c)) (setq x 'X) (setq z 'Z))    ; some
> > definitions entered inside emacs
>
> > (list 'list 'x 'y 'z)                                              ;
> > works with C-x C-e                      (1)
> > (eval (list 'list 'x 'y 'z))                                     ;
> > also works
> > `( (, list) list x y z)                                          ;
> > does not work though its same as (1)
>
> No, it's equivalent to:
>
> (list (list list) 'list 'x 'y 'z)
>
> which will probably get an error, since the variable "list" doesn't have
> a value.  Remember that Emacs Lisp has separate function and value
> bindings.

Maybe I did not explain very well. What is the equivalent to the
following in the backquote/unquote terminology.

(list 'list 'x 'y 'z)

Second,

' = quote
` = backquote
, = ??? in elisp

[Nick Keighley]

is

'(list x y z)

the answer?

[Pascal J. Bourguignon]

bolega <gnui...@gmail.com> writes:
> Maybe I did not explain very well. What is the equivalent to the
> following in the backquote/unquote terminology.
>
> (list 'list 'x 'y 'z)

There is no THE equivalent, there is an infinite number of backquote
forms that would be read as an expression evaluating to the same (by
equal) result than (list 'list 'x 'y 'z). Most probably, none of them
would read as (list 'list 'x 'y 'z), at least, the possibility would
depend on the implementation.

Here are four of them, but an infinite number of combinations are
possible:

`(list x y z)
`(,'list ,'x ,'y ,'z)
`(,'list ,@'(x y z))
`(,(intern (symbol-name 'list)) ,@'(x y z))

> Second,
>
> ' = quote
> ` = backquote
> , = ??? in elisp

unquote.

--
__Pascal Bourguignon__ http://www.informatimago.com/