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(backquote-process): Don't crash if ultimate

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expression is just a variable.
This commit is contained in:
Richard M. Stallman 1994-04-12 17:45:53 +00:00
parent c2a2858aec
commit cd320f323e
1 changed files with 20 additions and 7 deletions
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27
lisp/emacs-lisp/backquote.el
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@ -141,8 +141,18 @@ Vectors work just like lists. Nested backquotes are permitted."
((eq (car s) backquote-backquote-symbol)
(backquote-process (cdr (backquote-process (nth 1 s)))))
(t
(let ((rest s) (item nil) (firstlist nil) (list nil) (lists nil))
(let ((rest s)
item firstlist list lists expression)
;; Scan this list-level, setting LISTS to a list of forms,
;; each of which produces a list of elements
;; that should go in this level.
;; The order of LISTS is backwards.
;; If there are non-splicing elements (constant or variable)
;; at the beginning, put them in FIRSTLIST,
;; as a list of tagged values (TAG . FORM).
;; If there are any at the end, they go in LIST, likewise.
(while (consp rest)
;; Turn . (, foo) into (,@ foo).
(if (eq (car rest) backquote-unquote-symbol)
(setq rest (list (list backquote-splice-symbol (nth 1 rest)))))
(setq item (backquote-process (car rest)))
@ -158,20 +168,23 @@ Vectors work just like lists. Nested backquotes are permitted."
(t
(setq list (cons item list))))
(setq rest (cdr rest)))
;; Handle nonsplicing final elements, and the tail of the list
;; (which remains in REST).
(if (or rest list)
(setq lists (cons (backquote-listify list (backquote-process rest))
lists)))
(setq lists
;; Turn LISTS into a form that produces the combined list.
(setq expression
(if (or (cdr lists)
(and (consp (car lists))
(eq (car (car lists)) backquote-splice-symbol)))
(eq (car-safe (car lists)) backquote-splice-symbol))
(cons 'append (nreverse lists))
(car lists)))
;; Tack on any initial elements.
(if firstlist
(setq lists (backquote-listify firstlist (cons 1 lists))))
(if (eq (car lists) 'quote)
(setq expression (backquote-listify firstlist (cons 1 expression))))
(if (eq (car-safe expression) 'quote)
(cons 0 (list 'quote s))
(cons 1 lists))))))
(cons 1 expression))))))
;; backquote-listify takes (tag . structure) pairs from backquote-process
;; and decides between append, list, backquote-list*, and cons depending