On 22/09/2010 16:27, Anstis, Michael (M.) wrote:
Why the two different operators for in- and cross-pattern "or"
i.e. "||" and "or". What a pain that surely would be from a user
perspective...
At the moment you can use both 'or' and '||' infix between patterns,
probably becuse we couldn't decide what was best so added both. Inside
of patterns only '||' made sense. I think 'or' was added between
patterns to keep similarity to allow levels of comfort for Clips and
Jess users. In a way as other Conditional Elements are keywords removing
'||' between patterns and only using 'or' might be easier, it also helps
visually differentiate bewteen or inside of a pattern and outside. But
I'm also open to just using '||' everywhere for consistency, this is
something we need to decide and agree between us.
Where does that fit in with the language orthogonality too (blogged
about by Edson some time ago - sorry to drag the past up
http://tirelli.blogspot.com/2007/08/quick-catch-up-and-language.html)?
Simplying the language, removing redundanceis and special cases all
helps for that. Edsons work on generic expressions inside of patterns
helps remove a lot of cruft.
Mark
+1 for infix too :-)
I think it will be infix, that's what most people seem to prefer.
Mark
------------------------------------------------------------------------
*From:* [email protected]
[mailto:[email protected]] *On Behalf Of *Mark Proctor
*Sent:* 22 September 2010 16:03
*To:* [email protected]
*Subject:* Re: [rules-dev] Drools syntax diagrams - redrawn
On 22/09/2010 14:40, Wolfgang Laun wrote:
Service:
http://www-cgi.uni-regensburg.de/~brf09510/syntax.html
<http://www-cgi.uni-regensburg.de/%7Ebrf09510/syntax.html>
The grammar syntax is the same as used in DRL.g but stripped of
all the antsy additions, and simplified.
@Mark: I'm well aware of the limitations of a 1:1 translation of
a parser's grammar into diagrams. I have reduced the splits into
separate rules in DRL.g considerably. But what do you want to
hide from the users? The syntax is the syntax, and there's no
sweet-talking around it after you have reduced all the noise from
technical splits.
One thing that might help would be deprecating things like infix
or/and.
yes agreed. Simplifying the grammar, reducing ambigiiouty or
multiple ways of doing the same thing, will make any resulting
grammar both easier ot maintain and grok.
Edson, Davide and I have already discuss this. Both are working on
a new parser and are trying to address these issues. So things
that are doing are:
Single binding on 'or'
$binding : ( Pattern() || Pattern() )
We are thinking of only allowing 'or' between patterns and not
allowing users to mix and match 'or' and '||'. Inside of patterns
'||' is the only connective allowed and will remain so.
We will also probably make a choice and only allow infix 'or' and
'and', at the moment users can chose infix or prefix. Personally I
find prefix quite attractive as it works sort of like a "choice":
(or Person( ... )
Person( ... )
Person( ...) )
But I think most peopel are more comfortable with infix:
(Person( ... ) or
Person( ... ) or
Person( ...) )
return value, eval, literal constraint, variable constraint are
going. These are left overs of a Clips based grammar. So instead
we'll have a generic "expr" class that follow more common modern
ASTs for expression engines, like say MVEL.
Davide has also requested that we make $ prefix mandatory for LHS
bindings as that is deterministic and again makes the grammar
cleaner. I personally like it being optional and it's still open
to debate. But I recognise the need to have better maintained
grammar, that is more consistent and regular with easy to main
documentation.
Mark
Some rules can be omitted if they coincide with Java's own rules;
just add an explanation.
-W
On 22 September 2010 14:56, Anstis, Michael (M.)
<[email protected] <mailto:[email protected]>> wrote:
What was the service and was it the ANTLR grammar you uploaded to
generate the images?
Thanks,
Mike
-----Original Message-----
From: [email protected]
<mailto:[email protected]>
[mailto:[email protected]
<mailto:[email protected]>] On Behalf Of
Wolfgang Laun
Sent: 22 September 2010 13:38
To: Rules Dev List
Subject: [rules-dev] Drools syntax diagrams - redrawn
I've found this online service and stuffed the Drools grammar
into it.
You may see the results while they are still there:
http://www-cgi.uni-regensburg.de/~brf09510/syntax.tmp/x45371x0x0x.ebnf.h
tml
<http://www-cgi.uni-regensburg.de/%7Ebrf09510/syntax.tmp/x45371x0x0x.ebnf.h%0Atml>
<http://www-cgi.uni-regensburg.de/%7Ebrf09510/syntax.tmp/x45371x0x0x.ebn
f.html
<http://www-cgi.uni-regensburg.de/%7Ebrf09510/syntax.tmp/x45371x0x0x.ebn%0Af.html>>
-W
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