validating the grammar

Brendan Eich brendan at mozilla.org
Sat Sep 8 10:25:15 PDT 2012


Michael Dyck wrote:
> Allen Wirfs-Brock wrote:
>>
>> Another concern is that the entire grammar really needs to be 
>> revalidated
>> after major changes.  The last time the grammar was validated was for
>> ES3  (1999) and we don't currently have the tools or people in place to
>> validate it again (any volunteers out there??).
>
> What exactly do you mean by "validate the grammar"?

See http://lxr.mozilla.org/js/source/js2/semantics/ -- this is 
Waldemar's ES3-to-original-JS2/ES4-era grammar and semantics checking 
code, written in Mac Common Lisp.

> In the past, you mentioned "the committee's desire to have a generally
> LR(1) grammar", so I'm guessing "validation" = "confirmation that the
> grammar is [generally] LR(1)". Is it anything beyond that? Are the
> results of the ES3 grammar-validation archived somewhere? (Or are the
> results simply "Yes"?)

I recall Waldemar saying his code checks for unambiguous LR(1) after 
applying the lookahead restrictions and handling restricted productions 
([no LineTerminator here] rules for ASI). He said it checks other 
properties of the grammar, but I can't recall details right now. Cc'ing him.

/be


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