Re: Scheme Mode and Regular Expression Literals

[Mattias Engdegård]

>    (syntax-propertize-rules
> +    ;; For #/regexp/ syntax
> +    ("\\(#\\)/\\(\\\\/\\|\\\\\\\\\\|.\\)*?\\(/\\)"
> +     (1 "|")
> +     (3 "|"))

That amount of leaning toothpicks confuses even someone used to reading Elisp 
regexps so I'm switching notation here (`syntax-propertize-rules` permits 
regexps in rx). The above means:

  ((rx (group "#") "/"
       (*? (group (| "\\/" "\\\\" nonl)))
       (group "/"))
   (1 "|")
   (3 "|"))

This is a tad too ambiguous; it will match "#/ab\/", for instance, which 
probably wasn't intended.
What about the more robust

  ((rx (group "#") "/"
       (* (| (: "\\" nonl)
             (not (in "\n/\\"))))
       (group "/"))
   (1 "|")
   (2 "|"))

instead?

The Gauche documentation isn't entirely clear on how literal newlines are lexed 
inside this construct.
If newlines can be part of regexp literals, remove the \n from the third line.
If backslashed newlines are allowed, change `nonl` to `anychar`.