Re: [PATCH] Scheme-mode: Add support for regular expression literal

[Stefan Monnier]

> This patch against 'scheme.el' enables scheme-mode to handle regular
> expression literal #/regexp/ that is availabe in some Scheme
> implementations such as GNU Kawa [1] and Gauche [2].

Thanks, I was preparing to install the patch but then noticed that
I can't see your name in the list of people who signed the
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In the mean time, some comments on your patch:

>     (syntax-propertize-rules
>      ("\\(#\\);" (1 (prog1 "< cn"
> -                     (scheme-syntax-propertize-sexp-comment (point) end)))))
> +                     (scheme-syntax-propertize-sexp-comment (point) end))))
> +    ("\\(#\\)/" (1 (when (null (nth 8 (save-excursion
> +                                        (syntax-ppss
> +                                         (match-beginning 0)))))
> +                     (put-text-property
> +                      (match-beginning 0)
> +                      (1+ (match-beginning 0))
> +                      'syntax-table (string-to-syntax "|"))
> +                     (scheme-syntax-propertize-regexp
> +                      (point) end)
> +                     nil)
> +                   )))
>     (point) end))

The \\( and \\) around the # are there to create a subgroup 1, but you
don't actually make use of this subgroup.  So either:

- Remove those \\( and \\) since they're not needed (and change the "(1"
  to "(0"), or

- Replace (match-beginning 0) and (1+ (match-beginning 0)) with
  (match-beginning 1) and (match-end 1).

> +(defun scheme-syntax-propertize-regexp (_ end)

If you don't make use of the first arg, better remove it form here and
from your callers.

> +  (let* ((state (syntax-ppss))
> +         (within-str (nth 3 state))
> +         (start-delim-pos (nth 8 state)))
> +    (when (and within-str
> +               (char-equal ?# (char-after start-delim-pos)))
> +      (while
> +          (and
> +           (re-search-forward "/" end t)
> +           (eq -1
> +               (% (save-excursion
> +                    (backward-char)
> +                    (skip-chars-backward "\\\\")) 2))))
> +      (when (< (point) end)

This condition will be true when `search-forward` failed to find
a slash before `end` (I suspect this is what causes the problems that
Mattias saw).  One way to fix the problem is to pass `move` rather than
`t` as last argument to `search-forward`.


        Stefan


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