Re: [lojban] confusion over FUhE-post PEG grammar rule

[Jorge Llambías <jjllambias@gmail.com>]

On Mon, Jan 31, 2011 at 12:05 PM, .alyn.post.
<alyn.post@lodockikumazvati.org> wrote:
> I'm confused over the intent of the FUhE-post production in the PEG
> grammar:
>
> FUhE-clause <- FUhE-pre FUhE-post
> FUhE-pre    <- pre-clause FUhE spaces?
> FUhE-post   <- !BU-clause spaces? !ZEI-clause !BU-clause

Probably a remnant of an older version where it did something.

> The ! predicate does not advance the input, so if you walk through
> each rule in the FUhE-post production, you try to:
>
>  * not match BU-clause.  If we find one, we no-match This  immediately
>   and stop checking.  The input isn't advanced if we non-match it.

The idea is that "fu'e bu" will not match FUhE-clause.

I don't think this ever comes into play though. This applies to the
!BU-clause !ZEI-clause in post-clause as well. If I'm not mistaken
they ccould be removed.

>  * the spaces? production will always match the empty string, as
>   FUhE-post only appears in FUhE-clause, and FUhE-pre, the rule
>   before it, ends with a spaces?

This also applies to the spaces? in post-clause. If I'm not mistaken,
it never gets a chance to grab any spaces.

>  * not match ZEI-clause.  If we find ZEI-clause, we immediately
>   stop checking.  If we don't find one, the input is not advanced.
>  * not match BU-clause.  This is where I get confused.  We haven't
>   advanced the token stream, and we've already checked for a
>   BU-clause earlier.

Right, it's redundant. But I think even the first one is doing nothing.

> The final !BU-clause is either:
>
>  * redundant
>  * should be something like !(ZEI-clause BU-clause)

What for?

> Anything I missed?

Probably not. Remember that the PEG has never really been optimized,
and it has gone through some changes, especially concerning magic
words.

mu'o mi'e xorxes

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