Re: expected_function

> Am 17.06.2016 um 02:25 schrieb Joel de Guzman <[email protected]>:
>
>> On 15/06/2016 12:40 AM, Frank Hein wrote:
>>
>>>> Am 14.06.2016 um 07:20 schrieb Joel de Guzman <[email protected]>:
>>>>
>>>> On 14/06/2016 10:43 AM, Frank Hein wrote:
>>>> If you are still looking for an expect directive for qi 2
>>>>
>>>> https://github.com/mxc-commons/MxcQitoo
>>>
>>> Nice! Wouldn't it make sense if we just added this to Qi? ;-)
>>
>> Really? Feel free. :) Would be a great honor.
>
> We can probably do it in separate PRs, starting with the expect directive
> perhaps?

That's a good point to start with for me to get confident with the
procedures. I'd fork spirit, add the operator, move it into the qi
namespace, adjust example and test. Regarding the docs I'll have to look
how they are done. I'll take the existing directives doc as a spec. Ok so
far?

> That way, we can do a thorough review. Also, I'm not yet sure if
> all the additional components can make it into the codebase. expect is
> definitely an important addition. probe is interesting, but I'm not 100%
> sure about what it really is and its significance.

Probe does in effect the same as the existing hold directive. It does
attribute rollback if the expression fails to parse. Hold accomplishes that
by creating a temporary attribute and swapping that in on success. So it
requires swap to be implemented for the attribute type.

Probe on the other hand does not produce a temporary atrribute. It parses
lookahead once and on success a second time producing the attribute. No
swap implementation necessary. So it can be savely applied even on
intermediates like expr >> hold[expr] without having the intermediate
attribute type explicitly defined.

Pro hold: Parses once, no buffering, speed
Inconvenience: Swap impl. necessary
Effort: Parse (fail), parse + swap ( success)

Pro probe: No swap, applicable to intermediates
Cons: Lookahead
Effort: Parse ( fail), parse twice (success)

Probe is easier to use, so in parser development probe could be the choice,
while the final runtime optimized version would employ hold.


> operator / would be
> quite useful in certain contexts, but it can already be done using some
> other means, no?

It can be done otherwise.  id / string("::") can be expressed as id >>
*(string("id") >> id).
/ can parse a superset of %. So is id % expr the same as id / omit[expr]. /
does attribute rollback on failure.

> I'll also have to ask you to maintain your code and provide support for
> it. Oh and the docs will have to be properly integrated, just like any
> other component in Qi. So, in the end, it won't be an easy ride for you,
> but if you are willing to go the whole nine yards, then I am all for it.

Ok. My time is dedicated to tec research alone nowerdays. Live is a joy. :)
That's not all about parsing but I am willing to put effort in this.

> How about we go try it out with expect directive first? That is an easy
> one.

Yes, sure. Are the steps described above correct?

I have some other things ready, but I did not manage to finalize the docs
and tests before my vacation began. I am back in July. I extended qi to
support operators of higher arity. A ternary conditional operator called
if_ is available. This enables for example the Nabialek trick (just without
trick). I think, qitoo is a nice test bed for such proposals.

Looking forward to start. :)

Regards, Frank

>
> Regards,
> --
> Joel de Guzman
> http://www.ciere.com
> http://boost-spirit.com
> http://www.cycfi.com/
>
>
>
------------------------------------------------------------------------------

> What NetFlow Analyzer can do for you? Monitors network bandwidth and
traffic
> patterns at an interface-level. Reveals which users, apps, and protocols
are
> consuming the most bandwidth. Provides multi-vendor support for NetFlow,
> J-Flow, sFlow and other flows. Make informed decisions using capacity
planning
> reports. http://sdm.link/zohomanageengine
> _______________________________________________
> Spirit-general mailing list
> [email protected]
> https://lists.sourceforge.net/lists/listinfo/spirit-general
>

------------------------------------------------------------------------------
What NetFlow Analyzer can do for you? Monitors network bandwidth and traffic
patterns at an interface-level. Reveals which users, apps, and protocols are 
consuming the most bandwidth. Provides multi-vendor support for NetFlow, 
J-Flow, sFlow and other flows. Make informed decisions using capacity planning
reports. http://sdm.link/zohomanageengine

_______________________________________________
Spirit-general mailing list
[email protected]
https://lists.sourceforge.net/lists/listinfo/spirit-general