[ragel-users] Default actions that leave the machine

[Murray Henderson]

Hello,

Both local and global error actions transition to the error state. I
am using Ragel 6.5. I can try with 6.6 when I get home.

I made a quick example (based off S. Geist's example):

http://pastebin.com/06ihRxQg

Example output:

HELLO WORLD
read: HELLO WORLD
len: 12, state: 12
HELWORLD
parse error
read: HEL
len: 3, state: 0


Cheers,
Murray


On Tue, Feb 1, 2011 at 10:02 AM, Adrian Thurston <thurston at complang.org> wrote:
> 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
>>>>
>>>> _______________________________________________
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>>>> ragel-users at complang.org
>>>> http://www.complang.org/mailman/listinfo/ragel-users
>>>>
>>>
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>>
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