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(backquote-delay-process): New function.

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(backquote-process): Add internal arg `level'.  Use the two to
correctly handle nested backquotes.
This commit is contained in:
Stefan Monnier 2007-08-10 06:52:30 +00:00
parent 33e5d7d4c9
commit 3527bdcc43
1 changed files with 39 additions and 15 deletions
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54
lisp/emacs-lisp/backquote.el
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@ -118,10 +118,28 @@ Vectors work just like lists. Nested backquotes are permitted."
;; constant, 1 => to be unquoted, 2 => to be spliced in.
;; The top-level backquote macro just discards the tag.
(defun backquote-process (s)
(defun backquote-delay-process (s level)
"Process a (un|back|splice)quote inside a backquote.
This simply recurses through the body."
(let ((exp (backquote-listify (list (backquote-process (nth 1 s) level)
(cons 0 (list 'quote (car s))))
'(0))))
(if (eq (car-safe exp) 'quote)
(cons 0 (list 'quote s))
(cons 1 exp))))
(defun backquote-process (s &optional level)
"Process the body of a backquote.
S is the body. Returns a cons cell whose cdr is piece of code which
is the macro-expansion of S, and whose car is a small integer whose value
can either indicate that the code is constant (0), or not (1), or returns
a list which should be spliced into its environment (2).
LEVEL is only used internally and indicates the nesting level:
0 (the default) is for the toplevel nested inside a single backquote."
(unless level (setq level 0))
(cond
((vectorp s)
(let ((n (backquote-process (append s ()))))
(let ((n (backquote-process (append s ()) level)))
(if (= (car n) 0)
(cons 0 s)
(cons 1 (cond
@ -138,11 +156,15 @@ Vectors work just like lists. Nested backquotes are permitted."
s
(list 'quote s))))
((eq (car s) backquote-unquote-symbol)
(cons 1 (nth 1 s)))
(if (<= level 0)
(cons 1 (nth 1 s))
(backquote-delay-process s (1- level))))
((eq (car s) backquote-splice-symbol)
(cons 2 (nth 1 s)))
(if (<= level 0)
(cons 2 (nth 1 s))
(backquote-delay-process s (1- level))))
((eq (car s) backquote-backquote-symbol)
(backquote-process (cdr (backquote-process (nth 1 s)))))
(backquote-delay-process s (1+ level)))
(t
(let ((rest s)
item firstlist list lists expression)
@ -154,11 +176,13 @@ Vectors work just like lists. Nested backquotes are permitted."
;; 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)))
(while (and (consp rest)
;; Stop if the cdr is an expression inside a backquote or
;; unquote since this needs to go recursively through
;; backquote-process.
(not (or (eq (car rest) backquote-unquote-symbol)
(eq (car rest) backquote-backquote-symbol))))
(setq item (backquote-process (car rest) level))
(cond
((= (car item) 2)
;; Put the nonspliced items before the first spliced item
@ -168,8 +192,8 @@ Vectors work just like lists. Nested backquotes are permitted."
list nil))
;; Otherwise, put any preceding nonspliced items into LISTS.
(if list
(setq lists (cons (backquote-listify list '(0 . nil)) lists)))
(setq lists (cons (cdr item) lists))
(push (backquote-listify list '(0 . nil)) lists))
(push (cdr item) lists)
(setq list nil))
(t
(setq list (cons item list))))
@ -177,8 +201,8 @@ Vectors work just like lists. Nested backquotes are permitted."
;; 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)))
(push (backquote-listify list (backquote-process rest level))
lists))
;; Turn LISTS into a form that produces the combined list.
(setq expression
(if (or (cdr lists)
@ -221,5 +245,5 @@ Vectors work just like lists. Nested backquotes are permitted."
tail))
(t (cons 'list heads)))))
;;; arch-tag: 1a26206a-6b5e-4c56-8e24-2eef0f7e0e7a
;; arch-tag: 1a26206a-6b5e-4c56-8e24-2eef0f7e0e7a
;;; backquote.el ends here