Following your recommendation, I have altered the query to read as
follows:
my $grammar = q
{
<autotree>
disj : conj disjOp disj | conj
conj : term conjOp(?) conj | term
term : qualif(?) term2
term2 : brack | phrase | ident
brack : '(' disj ')'
phrase : '"' ident(s?) '"'
ident : /[a-zA-Z0-9]+/i
qualif : ident '='
conjOp : /AND/i #| ''
disjOp : /OR/i
};
This should fix the precedence issue with 'qualif'. However, this shows
the same misbehaviour
as when I tried it. Again, a query 'a or b' is interpreted as 'a AND or
AND b'.
Any ideas?
Jonas
Jonas Wolf/UK/[EMAIL PROTECTED]
21-05-04 09:16
To: "Ron D. Smith" <[EMAIL PROTECTED]>
cc: [EMAIL PROTECTED]
Subject: Re: grammar problems
I would like to parse boolean queries like the following:
<=> means the two queries represent the same structure
this and that <=> this that
this or that
a b or c d <=> (a b) or (c d) <=> (a and b) or (c and d)
"this phrase" word <=> "this phrase" and word
abstract = error or content = mistake <=> (abstract = error) or (content =
mistake)
...
I hope that clarifies things.
> conj : term conjOp(?) conj | term
Yes, that seems like a good alternative, I will have to try if it works.
Thanks, Jonas
> Hello,
>
> I recently downloaded the Parse::RecDescent package to parse
> boolean queries. I have several questions, not necessarily about
> the package itself, but rather about my grammar.
>
> I am currently using the following grammar:
>
> my $grammar = q
> {
> <autotree>
> disj : qualif(?) conj disjRec(s?)
> disjRec : disjOp conj
> conj : term conjRec(s?)
> conjRec : conjOp term
> term : brack | phrase | ident
> brack : '(' disj ')'
> phrase : '"' ident(s?) '"'
> ident : /[a-zA-Z0-9]+/i
> qualif : ident '='
> conjOp : /AND/i
> disjOp : /OR/i
> };
>
> I have several problems with this.
>
> Firstly, the precedence isn't quite what I want in 'qualif'. I would
> like 'ident' to bind tightly to whatever comes next to it. Currently
> it seems to associate it with the whole 'disj' that comes after.
You do not provide any examples of what you are trying to parse, which
would
help. IMHO what you mean by the above paragraph is not clear so I don't
know
what you "want".
>
> Secondly, I would like the 'conjOp' operator to be optional, and that
> the parser recognises this. This means a query for 'a b' would be
> interpreted as 'a AND b'. I tried replacing the conjOp rule with
> 'conjOp : /AND/i | ""', but this does not work, as now a query
> 'a AND b' is interpreted as 'a AND and ...'.
Perhaps:
conj : term conjOp(?) conj | term
It might help if you followed the example given in the PR::D POD more
closely.
>
> Any help would be appreciated.
>
> Thanks, Jonas.
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5000 W. Chandler Blvd.
Chandler, AZ 85226
