[antlr-interest] parsing just a subset of a grammar

[Alexander Kostikov]

Terence,

Is there an estimation when C# target would become available for ANTLR v4?
I would gladly switch to the newest bits but it doesn't seem like C#
output is currently possible.

-- Alexander


On Tue, Nov 20, 2012 at 10:08 AM, Terence Parr <parrt at cs.usfca.edu> wrote:
>
> On Nov 20, 2012, at 9:47 AM, Alexander Kostikov wrote:
>
>> Terence,
>>
>> Thank you for the fuzzy parsing advice.
>>
>> Fuzzy parsing seems to be the natural choice here. I've tried it
>> yesterday and it worked on a sample data. But when I tried to supply
>> some real file two things came up:
>>
>> 1) Parser became very loose. ANTLR no longer finds out cases when
>> input almost matches the acl rule. Fuzzy parsing via 'config: (acl |
>> .)* EOF' ignores all input that is not 100% described by the acl rule.
>> I understand that this is a conflicting goal but it looks like
>> swallow_to_semi technique from Ivan's email could bring benefits from
>> both fuzzy parsing and error handling by making grammar more verbose.
>
> I think it's very sensitive to how you write the grammar. I was very happy with the fuzzy Java parser as it wasn't loose at all. this is with v4
>>
>> 2) ANTLRWorks debugger took significant time to parse the real data.
>> It was about ~40 seconds per file compared to ~1 second when I'm using
>> my old regex-based parser. It was just a run under debugger and for a
>> different target language (I'm targeting CSharp3) but performance is a
>> valid concern for me. I don't want to have a speed regression when
>> porting from the current regex parser. If there would be no way of
>> doing quick parser I'll introduce an intermediate representation -
>> only the parsing speed from this intermediate representation would
>> matter.
>
> ah. you must be using v3. All bets are off.  v3 option fuzzy is very slow O(n^2)
>
> T