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On Jun 1, 2013, at 3:17 PM, Tim Hill <drtimhill@gmail.com> wrote:
> Interesting discussion. To my mind this shows why it's NOT always a good idea to make everything pure BNF. Sometimes plain old English does it better. I think the compromise in the Lua ref guide is pretty sensible.

I'm surprised that you came away with that conclusion from my experiences. The summary in my mind of what happened is:
* I tried to use the EBNF
* I found that I could not because it was not at all complete
* LHF and Roberto very graciously clarified some rules, some of which I overlooked in the prose, some of which are not in the Reference.
* I gave up in part because the EBNF was useless as-is for computer-based parsing, and had to settle for something far less rigorous, and far more error prone.

As before, I wholly agree that the prose is preferable for humans.
But I still maintain that a "complete" grammar that is not complete is not helpful for computers, and is not helpful for humans.

A proper, rigorous, exact (E)BNF or LPeg grammar is still desirable, IMHO.