Re: SMIE: defining a build.ninja grammar

[<tomas@tuxteam.de>]

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On Fri, Apr 07, 2023 at 05:18:27PM +0300, Konstantin Kharlamov wrote:
> I initially posted this on Emacs stackexchange, but in absence of replies decided to re-post on the mailing list as that's where usually people knowing how SMIE works hang out.

I have no idea of SMIE, but I think I can answer one of
your questions -- perhaps in a surprising way:

[...]

> 3. How to define newline as a separator? E.g. a `build` ends with a newline, and then follows a region of assignments. I tried using a `"\n"`, but I'm not sure if SMIE interprets the backslash, nor that a `\n` will work with other newline types.

[...]

> My last attempt is the grammar below. I had some other variants that worked incorrectly, but they were incomplete as well. For this post I created a more complete version, but it does not compile for me because it doesn't like `text` definition, it throws `Adjacent non-terminals: id text`.
> 
>     (defvar test-mode-smie-grammar
>       (smie-prec2->grammar
>        (smie-bnf->prec2
>         '((id)
>           (path) ;; TODO: define how it's different from `id'
>           (statements (statement)
>                       (statement "\n" statements))
>           (statement (top_decls) (variable))
>           (text (id text)
>                 (text "\n"))
>           (variable (id "=" text))
>           (build_title (path build_title)
>                        (path ":"))
>           (top_decls
>            ("rule" id)
>            ("build" build_title ":" text)
>            )
>           ))))

Those "\n" you have there are translated by the Lisp reader
(i.e. "early") into code point 0x0A. So this is what SMIE is
going to see.

Now, no idea whether it special-cases this into "whatever counts
as a newline"; I'd venture a guess that it doesn't. I'd expect
that if "your" newlines are more complex than a simple "\n",
you'll have to extend the lexer, as detailed in "Defining
Tokens" [1] in the manual.

Cheers

[1] Info menu "SMIE Lexer" or this URL, if you prefer the intertubes:
   https://www.gnu.org/software/emacs/manual/html_node/elisp/SMIE-Lexer.html

-- 
t

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