[ragel-users] Default actions that leave the machine

[Adrian Thurston]

Local error actions don't. Sorry I should have suggested just those.

On 11-01-31 02:58 PM, Murray Henderson wrote:
> Hello,
>
> Local and global error actions transition to the error state.
>
> I want DEF to transition to the next machine (ie. behave like a final
> state), not the error state.
>
> The parser I am writing is permissive, all input must be accepted (I
> never want to goto the error state).
>
> I do not wish to use manual goto recovery, because the parser is large
> and complex, such manual tracking is a lot of work and error prone.
>
> Cheers,
> Murray
>
>
>
> On Tue, Feb 1, 2011 at 4:58 AM, Adrian Thurston
> <adrian.thurston at esentire.com>  wrote:
>> Hi, have you looked at ragel's local and global error actions yet? These may
>> do what you want.
>>
>> -Adrian
>>
>> On 11-01-26 08:08 PM, Murray Henderson wrote:
>>>
>>> Hello,
>>>
>>> I want to embed a default action into a machine that leaves the
>>> machine (without using manual a jump inside the action).
>>>
>>> For simplicities sake, I will call this operator $^^ (since it is
>>> similar to the Local Error operator).
>>>
>>>
>>> Example:
>>>
>>> action parse_error {}
>>> helloworld = ('HELLO ' %^^parse_error) 'WORLD';
>>>
>>> Non-error inputs include:
>>> HELLO WORLD
>>> HELLOWORLD (parse_error action occurs on 'O' ->    'W' transition)
>>> HELLWORLD (parse_error action occurs on 'L' ->    'W' transition)
>>> HELWORLD (parse_error action occurs on 'L' ->    'W' transition)
>>> HEWORLD (parse_error action occurs on 'E' ->    'W' transition)
>>> HWORLD (parse_error action occurs on 'H' ->    'W' transition)
>>> WORLD (parse_error action occurs on ->    'W' transition)
>>>
>>>
>>> I can simulate the above behavior with the '?' operator, but that is
>>> laborious, and there are other ways of using $^^ that I suspect cannot
>>> be simulated.
>>>
>>>
>>> I want this operator because I am trying to make a liberal parser that
>>> accepts all possible input. (Every state must have a default action)
>>> .I am creating a html5 parser that uses regular machines for
>>> tokenizing, and scanners built from the regular machines for parsing.
>>> Yes, I am mad.
>>>
>>> I cannot use manual jumps, because I don't want to jump out of the
>>> scanners mid-token.
>>>
>>>
>>> I am willing to try and add this operator into Ragel myself. I have
>>> grabbed the source code and tracked my way to fsmap.cpp, where the new
>>> operator would be added.
>>>
>>> Before I continue...
>>> Is there already a way to achieve my desired behavior that I am not aware
>>> of?
>>> Would such an operator be worthwhile? Is it even possible?
>>> Is there any knowledge that could be imparted that would help me make a
>>> patch?
>>>
>>> If I do end up making a patch, for symmetry purposes I will make
>>> global/local and start/any/final etc versions of the operator.
>>>
>>> After a brief look through the source, it looks like I would need to
>>> mod the FsmAp::fillGaps() function, passing in a (separate object for
>>> each?) final state into the FsmAp::attachNewTrans() instead of NULL.
>>>
>>> Ragel is a wonderful program by the way, thank you for creating it.
>>>
>>> Cheers,
>>> Murray
>>>
>>> _______________________________________________
>>> ragel-users mailing list
>>> ragel-users at complang.org
>>> http://www.complang.org/mailman/listinfo/ragel-users
>>>
>>
>> _______________________________________________
>> ragel-users mailing list
>> ragel-users at complang.org
>> http://www.complang.org/mailman/listinfo/ragel-users
>>
>
> _______________________________________________
> ragel-users mailing list
> ragel-users at complang.org
> http://www.complang.org/mailman/listinfo/ragel-users

_______________________________________________
ragel-users mailing list
ragel-users at complang.org
http://www.complang.org/mailman/listinfo/ragel-users