[sf-perl] The SF Perl Raku Study Group, 03/28 at 1pm PDT

[Joseph Brenner]

That's interesting thinking... I've been playing around with the idea
over here, but haven't got it to work (it fails to parse):

https://github.com/doomvox/raku-study/blob/main/bin/2021mar28/doomfiles_browse_sequence-iii.raku

This version does work-- just using greedy matching on "stuff" makes
it use orders-of-magnitude less resources:

https://github.com/doomvox/raku-study/blob/main/bin/2021mar28/doomfiles_browse_sequence-ii.raku


And yes, I would guess that the non-greedy matching probably works
here because the following material is effectively pinned at the end
of the document.

Note that you should be able to run these scripts as written, provided
you also pull copies of these source files:

https://github.com/doomvox/raku-study/tree/main/dat/doomfiles



On 3/29/21, yary <not.com at gmail.com> wrote:
> Hi Joe & other Raku study group attendees,
>
> At the time I left, we were looking at a grammar with a speed-memory issue
> on large-ish files. I had a germ of an idea which I couldn't express, and
> from the meeting notes I see you have a simple fix *"by changing stuff
> regex (.\*?) to non-greedy (.\*)*" I suspect the greedy-optimization works
> because the thing after the "stuff" regex is near the end of the file. Thus
> if instead it was close to the beginning, it would have a similar issue
> with greedy and non-greedy would fix.
>
> With a night to sleep on it, the thing I was thinking & trying to say is
> that, in the specialized HTML-grammar you had, the decision points are all
> at left-brackets. By re-writing "stuff" so that it will only backtrack when
> it hits a bracket, I expect more speed-memory gains.
>
> How well does this perform vs the simple .* greedy fix?
>
>     regex stuff
>     { (  # capture stuff (positional capture might not be needed)
>         [               # Stuff is a group of either
>             \<          # a left-bracket decision point
>           ||            # or
>             <-[ \< ]>+: # a ratcheting string of non-decision points
>         ]*              # 0-many of those. Greedy or non-greedy both work?
>     ) }  # end capture, end regex
>
> This was harder to express verbally & in code than I expected!
>
> -y
>
>
> On Sun, Mar 28, 2021 at 4:23 PM Joseph Brenner <doomvox at gmail.com> wrote:
>
>> I did send this one out, but it doesn't seem that it went out exactly,
>> so let's try this one more time.   The Study Group is happening,
>> already in progress, though we'll be taking a break next week and
>> broadcasting a burning yule log with the soundtrack to Jesus Christ
>> Superstar.  (Just kidding)
>>
>>
>> Flaming Carrot, "Night Patrol" (1986) by Bob Burden:
>>
>>     I feel it rising now...
>>     ... like little bubbles...
>>     THE MOON IS FULL...
>>     ... in a full moon, your brain floats to top of your head...
>>     I feel it...
>>     beginning to boil...
>>     a lot will happen tonight.
>>
>> The Raku Study Group
>>
>> March 28, 2021  1pm in California, 8pm in the UK
>>
>> Zoom meeting link:
>>
>> https://us02web.zoom.us/j/81127128506?pwd=N0I5bkxUZTRLaWwxN2RJTGlsT254QT09
>>
>> Passcode: 4RakuRoll
>>
>> RSVPs are useful, though not needed:
>>   https://www.meetup.com/San-Francisco-Perl/events/277163968/
>> _______________________________________________
>> SanFrancisco-pm mailing list
>> SanFrancisco-pm at pm.org
>> https://mail.pm.org/mailman/listinfo/sanfrancisco-pm
>>
>