Hi Dmitiry,
I am not quite sure about this, but I think that something like the
following
grammar Foo;
options {output = AST;}
prog : line*
;
line : (ident)* rule^ LF;
ident : WS;
rule : RULE;
RULE : 'rule';
LF : '\n' '\r'?;
WS : ' ';
would generate an AST where each "rule" comes after a list of "idents"
(spaces in the case above).
So, when you are walking through the tree, you could count the number of
"ident" children before a rule.
I am not sure that this would cover your case (since I am a beginner in "the
ways of ANTLR").
Hope this helps!
Nikos
On Wed, Jul 15, 2009 at 12:51 AM, Dmitiry Nagirnyak <dna...@gmail.com>wrote:
> Hi Nick,
>
> Thanks. It shows some useful techniques.
> Main thing there is LEADING_WS.
>
> But it doesn't demonstrate how to choose different rule based on
> identation.
>
> For example something like this would do the job:
> indent : LEADING_WS rule ;
> LEADING_WS : (' ')*
> {
> if ( 0 == (getColumn() % sizeOfIndent)) {
> // We have matched the indent size - need to generate the node
> and follow on the indents
> // HOW TO 1: Add node to AST here?
> // HOW TO 2: Execute another rule?
> } // Otherwise consume the spaces
> }
> ;
>
> How those HOW TOs can be done?
>
> Cheers,
> Dmitriy.
> 2009/7/15 Nick Vlassopoulos <nvlassopou...@gmail.com>
>
> Sorry for reposting, but I copied the wrong link,
>>
>> http://www.antlr.org/grammar/1078018002577/python.tar.gz
>>
>> Nikos
>>
>>
>>
>>
>> On Tue, Jul 14, 2009 at 5:57 PM, Nick Vlassopoulos <
>> nvlassopou...@gmail.com> wrote:
>>
>>> Hi Dmitiry,
>>>
>>> I am not sure if this is what you are looking for, but you might want to
>>> have a look
>>> on how the python grammar handles identation.
>>> See for example:
>>> http://www.antlr.org/grammar/1200715779785/Python.g
>>>
>>> Best Regards,
>>>
>>> Nikos
>>>
>>>
>>> On Tue, Jul 14, 2009 at 5:43 PM, Dmitiry Nagirnyak
>>> <dna...@gmail.com>wrote:
>>>
>>>> Hi,
>>>>
>>>> I am researching possibility to parse HAML syntax to port it to .NET.
>>>> There is project call NHAML but uses Regular Expressions instead of regular
>>>> parser.
>>>> While it is working great it has certain limitations.
>>>>
>>>> So people start thinking about a real parser. And years ago I did some
>>>> wotks with ANTLR and have chance to revisit it.
>>>>
>>>> My question is about whitespaces.
>>>> In NHAML whitespaces are significant at the beginning of line.
>>>>
>>>> What I would like to have is this (star* for whitespace):
>>>>
>>>> %A
>>>> **%B
>>>> ****%B1
>>>> ****%B2
>>>> **%C
>>>> ****%C1
>>>>
>>>> It would correspond to the tree sam type of tree (A in the root; B,C -
>>>> second level nodes, B1,B22, C1 - third level nodes).
>>>>
>>>> It would be easy if the whitespaces would always be indented at the sane
>>>> number (here 2).
>>>> But this should be configurable. And even more, instead of whitespaces
>>>> there might be tabs. But let's skip this for now.
>>>>
>>>> So grammar like this (just a quick draft) won't satisfy that:
>>>> nhaml : line*
>>>> ;
>>>> line : indent? rule
>>>> ;
>>>> indent : WS WS indent? // How to consume different number of WSs
>>>> depending on provided settings?
>>>> ;
>>>> rule : ~WS (~NL)*
>>>> ;
>>>>
>>>> So the actual question is in rule "indent".
>>>> If I don't know required number of matches of WS during development, how
>>>> can I write grammar for that?
>>>>
>>>> Cheers,
>>>> Dmitriy Nagirnyak.
>>>>
>>>>
>>>> List: http://www.antlr.org/mailman/listinfo/antlr-interest
>>>> Unsubscribe:
>>>> http://www.antlr.org/mailman/options/antlr-interest/your-email-address
>>>>
>>>>
>>>
>>
>
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