-;;; smie.el --- Simple Minded Indentation Engine
+;;; smie.el --- Simple Minded Indentation Engine -*- lexical-binding: t -*-
;; Copyright (C) 2010-2011 Free Software Foundation, Inc.
;; - 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.
+;; - Permit EBNF-style notation.
+;; - If the grammar has conflicts, the only way is to make the lexer return
+;; different tokens for the different cases. This extra work performed by
+;; the lexer can be costly and unnecessary: we perform this extra work every
+;; time we find the conflicting token, regardless of whether or not the
+;; difference between the various situations is relevant to the current
+;; situation. E.g. we may try to determine whether a ";" is a ";-operator"
+;; or a ";-separator" in a case where we're skipping over a "begin..end" pair
+;; where the difference doesn't matter. For frequently occurring tokens and
+;; rarely occurring conflicts, this can be a significant performance problem.
+;; We could try and let the lexer return a "set of possible tokens
+;; plus a refinement function" and then let parser call the refinement
+;; function if needed.
+;; - Make it possible to better specify the behavior in the face of
+;; syntax errors. IOW provide some control over the choice of precedence
+;; levels within the limits of the constraints. E.g. make it possible for
+;; the grammar to specify that "begin..end" has lower precedence than
+;; "Module..EndModule", so that if a "begin" is missing, scanning from the
+;; "end" will stop at "Module" rather than going past it (and similarly,
+;; scanning from "Module" should not stop at a spurious "end").
;;; Code:
;; Maybe also add (or <elem1> <elem2>...) for things like
;; (exp (exp (or "+" "*" "=" ..) exp)).
;; Basically, make it EBNF (except for the specification of a separator in
- ;; the repetition).
+ ;; the repetition, maybe).
(let ((nts (mapcar 'car bnf)) ;Non-terminals
(first-ops-table ())
(last-ops-table ())
;; the trouble, and it lets the writer of the BNF
;; be a bit more sloppy by skipping uninteresting base
;; cases which are terminals but not OPs.
- (assert (not (member (cadr rhs) nts)))
+ (when (member (cadr rhs) nts)
+ (error "Adjacent non-terminals: %s %s"
+ (car rhs) (cadr rhs)))
(pushnew (cadr rhs) first-ops)))
(let ((shr (reverse rhs)))
(if (not (member (car shr) nts))
(pushnew (car shr) last-ops)
(pushnew (car shr) last-nts)
(when (consp (cdr shr))
- (assert (not (member (cadr shr) nts)))
+ (when (member (cadr shr) nts)
+ (error "Adjacent non-terminals: %s %s"
+ (cadr shr) (car shr)))
(pushnew (cadr shr) last-ops)))))
(push (cons nt first-ops) first-ops-table)
(push (cons nt last-ops) last-ops-table)
(save-excursion (indent-line-to indent))
(indent-line-to indent)))))
+(defun smie-auto-fill ()
+ (let ((fc (current-fill-column))
+ (try-again nil))
+ (while (and fc (> (current-column) fc))
+ (cond
+ ((not (or (nth 8 (save-excursion
+ (syntax-ppss (line-beginning-position))))
+ (nth 8 (syntax-ppss))))
+ (save-excursion
+ (beginning-of-line)
+ (smie-indent-forward-token)
+ (let ((bsf (point))
+ (gain 0)
+ curcol)
+ (while (<= (setq curcol (current-column)) fc)
+ ;; FIXME? `smie-indent-calculate' can (and often will)
+ ;; return a result that actually depends on the presence/absence
+ ;; of a newline, so the gain computed here may not be accurate,
+ ;; but in practice it seems to works well enough.
+ (let* ((newcol (smie-indent-calculate))
+ (newgain (- curcol newcol)))
+ (when (> newgain gain)
+ (setq gain newgain)
+ (setq bsf (point))))
+ (smie-indent-forward-token))
+ (when (> gain 0)
+ (setq try-again)
+ (goto-char bsf)
+ (newline-and-indent)))))
+ (t (do-auto-fill))))))
+
+
(defun smie-setup (grammar rules-function &rest keywords)
"Setup SMIE navigation and indentation.
GRAMMAR is a grammar table generated by `smie-prec2->grammar'.
(set (make-local-variable 'smie-rules-function) rules-function)
(set (make-local-variable 'smie-grammar) grammar)
(set (make-local-variable 'indent-line-function) 'smie-indent-line)
+ (set (make-local-variable 'normal-auto-fill-function) 'smie-auto-fill)
(set (make-local-variable 'forward-sexp-function)
'smie-forward-sexp-command)
(while keywords