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is PetitParser eager by default?

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Peter Uhnak

is PetitParser eager by default?

Is PetitParser eager by default?

I've used PetitParser countless times so I am really baffled why this doesn't work

str := 'a0b'.
#any asParser star, #digit asParser, #any asParser star parse: str.

-> PPFailure (input expected at: 3)

Thanks,
Peter

Guillaume Larcheveque

Re: is PetitParser eager by default?

Yes, the #any asParser star consume all your stream.

for your example you can do:

str := 'a0b'.

#digit asParser negate star, #digit asParser, #any asParser star parse: str.

2017-01-20 15:24 GMT+01:00 Peter Uhnak <[hidden email]>:

Is PetitParser eager by default?

I've used PetitParser countless times so I am really baffled why this doesn't work

str := 'a0b'.
#any asParser star, #digit asParser, #any asParser star parse: str.

-> PPFailure (input expected at: 3)

Thanks,
Peter

Guillaume Larcheveque

NorbertHartl

Re: is PetitParser eager by default?

In reply to this post by Peter Uhnak

> Am 20.01.2017 um 15:24 schrieb Peter Uhnak <[hidden email]>:
>
> Is PetitParser eager by default?
>
> I've used PetitParser countless times so I am really baffled why this doesn't work
>
> str := 'a0b'.
> #any asParser star, #digit asParser, #any asParser star parse: str.
>
> -> PPFailure (input expected at: 3)
>

PetitParser is not greedy per default. But back tracking only works if a parser fails. Using , creates a sequence of combined parsers. If one fails the whole sequence fails. As a star parser always succeeds it would be huge luck if your rule would succeed. The probability that the parser consumes exactly one character is not high. Maybe negating the first sequence part is what you want

Norbert

Tudor Girba-2

Re: is PetitParser eager by default?

Hi,

When you have questions like these, you can also use the built-in debugging facilities. For example, in your case, you can see that the #any parser consumed everything like this:

Cheers,

Doru

On Jan 20, 2017, at 4:38 PM, Norbert Hartl <[hidden email]> wrote:

Am 20.01.2017 um 15:24 schrieb Peter Uhnak <[hidden email]>:

Is PetitParser eager by default?

I've used PetitParser countless times so I am really baffled why this doesn't work

str := 'a0b'.
#any asParser star, #digit asParser, #any asParser star parse: str.

-> PPFailure (input expected at: 3)

PetitParser is not greedy per default. But back tracking only works if a parser fails. Using , creates a sequence of combined parsers. If one fails the whole sequence fails. As a star parser always succeeds it would be huge luck if your rule would succeed. The probability that the parser consumes exactly one character is not high. Maybe negating the first sequence part is what you want

Norbert

--
www.tudorgirba.com
www.feenk.com

"What we can governs what we wish."

Peter Uhnak

Re: is PetitParser eager by default?

On Fri, Jan 20, 2017 at 04:57:51PM +0100, Tudor Girba wrote:
> Hi,
>
> When you have questions like these, you can also use the built-in debugging facilities. For example, in your case, you can see that the #any parser consumed everything like this:

Ah, thanks. I was looking for this in the debugger (because I remember there was some extension related to PetitParser) and completely missed it in the playground.

> >> Am 20.01.2017 um 15:24 schrieb Peter Uhnak <[hidden email]>:
> >>
> >> Is PetitParser eager by default?
> >>
> >> I've used PetitParser countless times so I am really baffled why this doesn't work
> >>
> >> str := 'a0b'.
> >> #any asParser star, #digit asParser, #any asParser star parse: str.
> >>
> >> -> PPFailure (input expected at: 3)
> >>
> >
> > PetitParser is not greedy per default. But back tracking only works if a parser fails. Using , creates a sequence of combined parsers. If one fails the whole sequence fails. As a star parser always succeeds it would be huge luck if your rule would succeed. The probability that the parser consumes exactly one character is not high. Maybe negating the first sequence part is what you want

This is not just about one character.

s := 'hello 123 world'.
#any asParser star , #digit asParser plus , #any asParser star parse: s.

But from your explanation my understanding is that this is actually not possible with #any.
Basically I was looking for the PetitParser equivalent of .*?\d+.* regex (note that even in greedy form the regex wouldn't fail because it would leave the last digit for \d)

Peter

stepharong

Re: is PetitParser eager by default?

In reply to this post by Tudor Girba-2

Hi doru

where do we see it?

Stef

On Fri, 20 Jan 2017 16:57:51 +0100, Tudor Girba <[hidden email]> wrote:

Hi,

When you have questions like these, you can also use the built-in debugging facilities. For example, in your case, you can see that the #any parser consumed everything like this:

Cheers,
Doru

On Jan 20, 2017, at 4:38 PM, Norbert Hartl <[hidden email]> wrote:

Am 20.01.2017 um 15:24 schrieb Peter Uhnak <[hidden email]>:

Is PetitParser eager by default?

I've used PetitParser countless times so I am really baffled why this doesn't work

str := 'a0b'.
#any asParser star, #digit asParser, #any asParser star parse: str.

-> PPFailure (input expected at: 3)

PetitParser is not greedy per default. But back tracking only works if a parser fails. Using , creates a sequence of combined parsers. If one fails the whole sequence fails. As a star parser always succeeds it would be huge luck if your rule would succeed. The probability that the parser consumes exactly one character is not high. Maybe negating the first sequence part is what you want

Norbert

--
www.tudorgirba.com
www.feenk.com

"What we can governs what we wish."

Using Opera's mail client: http://www.opera.com/mail/

Tudor Girba-2

Re: is PetitParser eager by default?

Hi,

The inspector shows the PPFailure, and the Debug View presentation of PPFailure shows you the paths the parser tried.

star produces a PPPossessiveRepeatingParser, and selecting it shows that it matched all three characters: they are selected in the bottom pane which shows the input string.

Cheers,
Doru

> On Jan 21, 2017, at 11:26 AM, stepharong <[hidden email]> wrote:
>
> Hi doru
>
> where do we see it?
>
>
> Stef
>
> On Fri, 20 Jan 2017 16:57:51 +0100, Tudor Girba <[hidden email]> wrote:
>
> Hi,
>
> When you have questions like these, you can also use the built-in debugging facilities. For example, in your case, you can see that the #any parser consumed everything like this:
>
> <Mail Attachment.png>
>
> Cheers,
> Doru
>
>
>> On Jan 20, 2017, at 4:38 PM, Norbert Hartl <[hidden email]> wrote:
>>
>>
>>> Am 20.01.2017 um 15:24 schrieb Peter Uhnak <[hidden email]>:
>>>
>>> Is PetitParser eager by default?
>>>
>>> I've used PetitParser countless times so I am really baffled why this doesn't work
>>>
>>> str := 'a0b'.
>>> #any asParser star, #digit asParser, #any asParser star parse: str.
>>>
>>> -> PPFailure (input expected at: 3)
>>>
>>
>> PetitParser is not greedy per default. But back tracking only works if a parser fails. Using , creates a sequence of combined parsers. If one fails the whole sequence fails. As a star parser always succeeds it would be huge luck if your rule would succeed. The probability that the parser consumes exactly one character is not high. Maybe negating the first sequence part is what you want
>>
>> Norbert
>>
>>
>
> --
> www.tudorgirba.com
> www.feenk.com
>
> "What we can governs what we wish."
>
>
>
>
>
>
>
> --
> Using Opera's mail client: http://www.opera.com/mail/

--
www.tudorgirba.com
www.feenk.com

“The smaller and more pervasive the hardware becomes, the more physical the software gets."

stepharong

Re: is PetitParser eager by default?

tx

On Sat, 21 Jan 2017 18:09:32 +0100, Tudor Girba <[hidden email]>
wrote:

> Hi,
>
> The inspector shows the PPFailure, and the Debug View presentation of
> PPFailure shows you the paths the parser tried.
>
> star produces a PPPossessiveRepeatingParser, and selecting it shows that
> it matched all three characters: they are selected in the bottom pane
> which shows the input string.
>
> Cheers,
> Doru
>
>
>> On Jan 21, 2017, at 11:26 AM, stepharong <[hidden email]> wrote:
>>
>> Hi doru
>>
>> where do we see it?
>>
>>
>> Stef
>>
>> On Fri, 20 Jan 2017 16:57:51 +0100, Tudor Girba <[hidden email]>
>> wrote:
>>
>> Hi,
>>
>> When you have questions like these, you can also use the built-in
>> debugging facilities. For example, in your case, you can see that the
>> #any parser consumed everything like this:
>>
>> <Mail Attachment.png>
>>
>> Cheers,
>> Doru
>>
>>
>>> On Jan 20, 2017, at 4:38 PM, Norbert Hartl <[hidden email]> wrote:
>>>
>>>
>>>> Am 20.01.2017 um 15:24 schrieb Peter Uhnak <[hidden email]>:
>>>>
>>>> Is PetitParser eager by default?
>>>>
>>>> I've used PetitParser countless times so I am really baffled why this
>>>> doesn't work
>>>>
>>>> str := 'a0b'.
>>>> #any asParser star, #digit asParser, #any asParser star parse: str.
>>>>
>>>> -> PPFailure (input expected at: 3)
>>>>
>>>
>>> PetitParser is not greedy per default. But back tracking only works if
>>> a parser fails. Using , creates a sequence of combined parsers. If one
>>> fails the whole sequence fails. As a star parser always succeeds it
>>> would be huge luck if your rule would succeed. The probability that
>>> the parser consumes exactly one character is not high. Maybe negating
>>> the first sequence part is what you want
>>>
>>> Norbert
>>>
>>>
>>
>> --
>> www.tudorgirba.com
>> www.feenk.com
>>
>> "What we can governs what we wish."
>>
>>
>>
>>
>>
>>
>>
>> --
>> Using Opera's mail client: http://www.opera.com/mail/
>
> --
> www.tudorgirba.com
> www.feenk.com
>
> “The smaller and more pervasive the hardware becomes, the more physical
> the software gets."
>

--
Using Opera's mail client: http://www.opera.com/mail/