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* lisp/emacs-lisp/smie.el (smie-prec2->grammar): Obey equality constraints

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when filling the remaining "unconstrained" values.
This commit is contained in:
Stefan Monnier 2010-11-11 20:33:28 -05:00
parent acef0722fc
commit 10b40d2ef6
2 changed files with 45 additions and 5 deletions
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5
lisp/ChangeLog
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@ -1,3 +1,8 @@
2010-11-12 Stefan Monnier <monnier@iro.umontreal.ca>
* emacs-lisp/smie.el (smie-prec2->grammar): Obey equality constraints
when filling the remaining "unconstrained" values.
2010-11-11 Stefan Monnier <monnier@iro.umontreal.ca>
* emacs-lisp/bytecomp.el (byte-compile-warnings): Simplify the

45
lisp/emacs-lisp/smie.el
View file

@ -74,10 +74,20 @@
;; IF=ELSE and ELSE=END, we could turn them into IF<ELSE and ELSE>END
;; and IF=END,
;;; Code:
;; TODO & BUGS:
;;
;; - FIXME: I think the behavior on empty lines is wrong. It shouldn't
;; look at the next token on subsequent lines.
;; - Using the structural information SMIE gives us, it should be possible to
;; implement a `smie-align' command that would automatically figure out what
;; there is to align and how to do it (something like: align the token of
;; lowest precedence that appears the same number of times on all lines,
;; and then do the same on each side of that token).
;; - Maybe accept two juxtaposed non-terminals in the BNF under the condition
;; that the first always ends with a terminal, or that the second always
;; starts with a terminal.
;; FIXME: I think the behavior on empty lines is wrong. It shouldn't
;; look at the next token on subsequent lines.
;;; Code:
(eval-when-compile (require 'cl))
@ -401,6 +411,18 @@ CSTS is a list of pairs representing arcs in a graph."
(append names (list (car names)))
" < ")))
;; (defun smie-check-grammar (grammar prec2 &optional dummy)
;; (maphash (lambda (k v)
;; (when (consp k)
;; (let ((left (nth 2 (assoc (car k) grammar)))
;; (right (nth 1 (assoc (cdr k) grammar))))
;; (when (and left right)
;; (cond
;; ((< left right) (assert (eq v '<)))
;; ((> left right) (assert (eq v '>)))
;; (t (assert (eq v '=))))))))
;; prec2))
(put 'smie-prec2->grammar 'pure t)
(defun smie-prec2->grammar (prec2)
"Take a 2D precedence table and turn it into an alist of precedence levels.
@ -469,6 +491,7 @@ PREC2 is a table as returned by `smie-precs->prec2' or
;; left = right).
(unless (caar cst)
(setcar (car cst) i)
;; (smie-check-grammar table prec2 'step1)
(incf i))
(setq csts (delq cst csts))))
(unless progress
@ -478,8 +501,19 @@ PREC2 is a table as returned by `smie-precs->prec2' or
(incf i 10))
;; Propagate equalities back to their source.
(dolist (eq (nreverse eqs))
(assert (or (null (caar eq)) (eq (car eq) (cdr eq))))
(setcar (car eq) (cadr eq)))
(when (null (cadr eq))
;; There's an equality constraint, but we still haven't given
;; it a value: that means it binds tighter than anything else,
;; and it can't be an opener/closer (those don't have equality
;; constraints).
;; So set it here rather than below since doing it below
;; makes it more difficult to obey the equality constraints.
(setcar (cdr eq) i)
(incf i))
(assert (or (null (caar eq)) (eq (caar eq) (cadr eq))))
(setcar (car eq) (cadr eq))
;; (smie-check-grammar table prec2 'step2)
)
;; Finally, fill in the remaining vars (which only appeared on the
;; right side of the < constraints).
(let ((classification-table (gethash :smie-open/close-alist prec2)))
@ -500,6 +534,7 @@ PREC2 is a table as returned by `smie-precs->prec2' or
(incf i))))) ;See other (incf i) above.
(let ((ca (gethash :smie-closer-alist prec2)))
(when ca (push (cons :smie-closer-alist ca) table)))
;; (smie-check-grammar table prec2 'step3)
table))
;;; Parsing using a precedence level table.