Re: Help with grammar
Thank you all for your replies.
I was able to fix it and better understanding grammars :-)
Regards,
David Santiago
Patrick R. Michaud escreveu no dia quinta,
21/05/2020 Ã (s) 21:05:
>
> On Thu, May 21, 2020 at 08:40:08PM +, David Santiago wrote:
> > Can someone explain me why my grammar isn't working? Unfortunately i
> > can't figure it out :-(
> >
> > | headers
> > | | header
> > | | * MATCH "Proxy-Connection"
> > | | header-value
> > | | * MATCH "keep-alive\n"
> > | | crlf
> > | | * FAIL
> > | * FAIL
> > * FAIL
> > Nil
>
> Notice how is capturing the newline in "keep-alive\n"? That
> means there's not a newline for the <.crlf> subrule that follows, and thus
> the match fails.
>
> Try changing "rule header-value" to be a "token" instead. That will prevent
> it from consuming any whitespace immediately following the + sequence.
> When I tried your script with header-value defined as a token, it got a lot
> farther into the match:
>
> $ rakudo test.raku
> TOP
> | request-line
> | | method
> | | * MATCH "CONNECT"
> | | request-uri
> | | * MATCH "ssl.gstatic.com:443"
> | | http-version
> | | * MATCH "HTTP/1.1"
> | | crlf
> | | * MATCH "\n"
> | * MATCH "CONNECT ssl.gstatic.com:443 HTTP/1.1\n"
> | headers
> | | header
> | | * MATCH "Proxy-Connection"
> | | header-value
> | | * MATCH "keep-alive"
> | | crlf
> | | * MATCH "\n"
> | * MATCH "Proxy-Connection: keep-alive\n"
> * MATCH "CONNECT ssl.gstatic.com:443 HTTP/1.1\nProxy-Connection: keep-"
> Nil
>
>
> Personally, I would likely define to be something more like
>
> token header-value { \N+ }
>
> which gets any sequence of non-newline characters, since some of the headers
> coming afterwards contain spaces and characters which aren't part of .
>
> Pm
Re: Help with grammar
On Thu, May 21, 2020 at 08:40:08PM +, David Santiago wrote:
> Can someone explain me why my grammar isn't working? Unfortunately i
> can't figure it out :-(
>
> | headers
> | | header
> | | * MATCH "Proxy-Connection"
> | | header-value
> | | * MATCH "keep-alive\n"
> | | crlf
> | | * FAIL
> | * FAIL
> * FAIL
> Nil
Notice how is capturing the newline in "keep-alive\n"? That
means there's not a newline for the <.crlf> subrule that follows, and thus the
match fails.
Try changing "rule header-value" to be a "token" instead. That will prevent it
from consuming any whitespace immediately following the + sequence.
When I tried your script with header-value defined as a token, it got a lot
farther into the match:
$ rakudo test.raku
TOP
| request-line
| | method
| | * MATCH "CONNECT"
| | request-uri
| | * MATCH "ssl.gstatic.com:443"
| | http-version
| | * MATCH "HTTP/1.1"
| | crlf
| | * MATCH "\n"
| * MATCH "CONNECT ssl.gstatic.com:443 HTTP/1.1\n"
| headers
| | header
| | * MATCH "Proxy-Connection"
| | header-value
| | * MATCH "keep-alive"
| | crlf
| | * MATCH "\n"
| * MATCH "Proxy-Connection: keep-alive\n"
* MATCH "CONNECT ssl.gstatic.com:443 HTTP/1.1\nProxy-Connection: keep-"
Nil
Personally, I would likely define to be something more like
token header-value { \N+ }
which gets any sequence of non-newline characters, since some of the headers
coming afterwards contain spaces and characters which aren't part of .
Pm
Re: Help with grammar
On 2020-05-21 David Santiago wrote:
> Can someone explain me why my grammar isn't working? Unfortunately i
> can't figure it out :-(
Mixing ``rule``, ``token``, and ``regex`` apparently at random doesn't
make for a good grammar…
The text at
https://docs.raku.org/language/grammar_tutorial#The_technical_overview
is a bit confusing.
This https://docs.raku.org/language/regexes#Sigspace is more precise:
a ``rule`` inserts a ``<.ws>`` wherever there's whitespace in the
source code, so your::
rule header-value { + }
is equivalent to::
token header-value { + <.ws> }
which, as you saw in the trace, eats up the newline.
Short version: the only ``rule``s should be ``TOP``, ``request-line``,
and ``headers``, the others are all ``token``s
Extending the grammar to recognise more than one header is left as an
exercise.
--
Dakkar -
GPG public key fingerprint = A071 E618 DD2C 5901 9574
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Help with grammar
Hi! Can someone explain me why my grammar isn't working? Unfortunately i can't figure it out :-( Full script attached (42 lines) - the new lines in the script are always only "\n" The output: TOP | request-line | | method | | * MATCH "CONNECT" | | request-uri | | * MATCH "ssl.gstatic.com:443" | | http-version | | * MATCH "HTTP/1.1" | | crlf | | * MATCH "\n" | * MATCH "CONNECT ssl.gstatic.com:443 HTTP/1.1\n" | headers | | header | | * MATCH "Proxy-Connection" | | header-value | | * MATCH "keep-alive\n" | | crlf | | * FAIL | * FAIL * FAIL Nil It matches the request line's newline but not the headers. Best regards, David Santiago test.raku Description: Binary data
