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Re: [ELPA] New package: bnf-mode

From: Serghei Iakovlev
Subject: Re: [ELPA] New package: bnf-mode
Date: Sun, 05 May 2019 17:56:29 +0300
User-agent: Gnus/5.13 (Gnus v5.13) Emacs/26.2 (gnu/linux)

Hello Stefan,

Thank you for the review.  I've removed wrongly used (and documented)
`syntax-propertize-function' funcall.  Thank you for clarifying it
out.  As for the question: BNF is a notation technique for context
free grammars, often used to describe the syntax of languages used
in computing, such as programming languages, document formats,
instruction sets and communication protocols.

And I have to say than Bison is not BNF.  Probable you're meant yacc,
which is from 197x.  However BNF is designed (in 1959) to create
formal grammars in a formal language, what is not a subject area for
yacc or bison.  Yes, yacc, antlr, bison, META II, etc.  All they use
a dialect slightly reminiscent of BNF, but the do not use pure BNF
grammar.  In addition, they don't use a formal language.

I've updated the code in the repository but still not sure what
exactly should I attach on this reply.

Best regards,

Stefan Monnier <address@hidden> writes:
>> I created a major mode for editing BNF grammars [1] and would like to
>> add this package to the ELPA [2].  Currently it provides basic syntax
>> and font-locking for BNF files.  BNF notation is supported exactly
>> form as it was first announced in the ALGOL 60 report.  EBNF and ABNF
>> are not supported but in my plans for the near future.
> In what kind of circumstances would this be used?
> I've seen BNF-like syntax used by various tools (like bison and
> friends, for example), but never with this particular syntax.
>     ;; Basically `syntax-propertize-function' is a construct which belongs
>     ;; to `font-lock'.
> No.  It's used by font-lock (as well as various other things), but it
> does not belong to it.
>     ;; But correct indentation depends on
>     ;; syntax properties of the text, and that should ideally be
>     ;; independent of font-lock being activated or not.
> Which is why syntax-propertize was created (as opposed to the previous
> font-lock-syntactic-keywords, which *did* belong to font-lock and
> suffered from the problem you describe).
>     ;; For `bnf-mode', this means that with `font-lock' disabled, we wont
>     ;; have our syntax properties set correctly, and indentation will
>     ;; suffer.
> That's not true.
>     ;; To patch our way around this, we issue a `syntax-propertize' call
>     ;; manually, `font-lock' enabled or not.
>     (with-silent-modifications
>       (when bnf-mode-algol-comments-style
>         (funcall syntax-propertize-function (point-min) (point-max))))
> Don't do that: syntax-propertize-function will be called when needed
> (e.g. by indent-according-to-mode).
>         Stefan
<#secure method=pgpmime mode=encrypt>

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