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Re: Scheme Mode and Regular Expression Literals

From: Stefan Monnier
Subject: Re: Scheme Mode and Regular Expression Literals
Date: Thu, 14 Mar 2024 09:34:10 -0400
User-agent: Gnus/5.13 (Gnus v5.13)

>   ((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`.

If they can span several lines then matching the whole #/.../ with
a regexp is definitely the wrong approach.

If not, that rule can be made to work but it has to check that the
leading #/ is not inside a string or comment.

The more robust approach is to match only #/ here and then use
a function which checks the resulting `syntax-ppss` to handle the rest
of the regexp.

See `octave-syntax-propertize-function` for an example of the structure
where we use the regexp "\\(?:^\\|[[({,; ]\\)\\('\\)" to match the
beginning of a quoted string, and then use
`octave-syntax-propertize-sqs` to process its contents (and use that as
well at the beginning of the function in case `syntax-propertize` is
called with start in the middle of such a string (or in our case,


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