Date:         Mon, 1 Dec 2003 12:25:45 +0100
Reply-To:     "Z39.50 Next-Generation Initiative" <[log in to unmask]>
Sender:       "Z39.50 Next-Generation Initiative" <[log in to unmask]>
From:         Adam Dickmeiss <[log in to unmask]>
Subject:      Re: New proposed grammar for CQL (revised from Yacc grammar)
Comments: To: "Z39.50 Next-Generation Initiative" <[log in to unmask]>
In-Reply-To:  <[log in to unmask]>
Content-Type: text/plain; charset=us-ascii; format=flowed

Robert Sanderson wrote:

>>If it's the last grammar you put up, it is unabiguous which is good.
>>And, yes, it doesn't allow
>> >p1 b and >p2 c
>>I can live with that. Especially, since
>> >p1 b and/a>p2 c
>>would be ambiguous - and hard to read. To achive this with Alan's
>>grammar you would have to use
>> >p1 and/a (>p2 c)
>>
>>
>
>Can parsers have a rule (not in the BNF) that makes /a>b always a single
>modifier, rather than a modifier and a prefix?
>
>
Well, if I use my grammar and let YACC use it, it will choose that
automatically.

>Making /a >b=c a parse error, but it would be in the BNF anyway as it's
>not ()ed, so you're not losing anything?
>
>
Don't know what you mean? What BNF? Alan's? Mine?

Alan's BNF disallows a prefix specification following a boolean operator
(no matter what). So anything following a boolean operator will be
treated as a modifier.

The YACC grammar allows both, but is ambiguous - still works in an
implementation since YACC chooses the right thing - when a conflict arises.

I propose we choose Alans unambiguous BNF as the spec.

-- Adam

>Rob
>
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