[antlr-interest] Parsing HAML - significant and insignificant whitespaces

[Nick Vlassopoulos]

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
<nvlassopoulos at 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 <dnagir at 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.
>>
>>
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>>
>
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