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norswap
autumn
Java2017–2021
norswap / autumn

autumn

A Java parser combinator library written with an unmatched feature set.

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6Distinct people
8Mentions
0Explicit recommenders
132GitHub stars
REPOSITORY AT A GLANCE

What to know before exploring

What it is

A Java parser combinator library written with an unmatched feature set.

GitHub

Where it is used

No documented product use has been verified yet.

What people are saying

No recommendation phrase was found in the indexed comments.

No classified warning is attached to this page. Read the discussions before treating silence as approval.

Also in these discussions

No other repository is repeatedly linked in the same discussions.

This week on Hacker News

Nov 7–Nov 14 UTC · Direct repository links and separately labeled related project stories. Indexed through 11/14/2026, 5:04:57 PM UTC.

No direct repository links were found in the indexed HN discussions over the past seven days. Older discussions are available below.

Mentions over time

HN mentions by year8 dated mentions

Observed mentions: 2017-03-23 23:28:38 UTC to 2021-05-14 05:24:40 UTC.

01232017-01-01 00:00:00 UTC to 2018-01-01 00:00:00 UTC (exclusive): 1 mentions; 0 submissions, 1 comments20172018-01-01 00:00:00 UTC to 2019-01-01 00:00:00 UTC (exclusive): 1 mentions; 1 submissions, 0 comments2019-01-01 00:00:00 UTC to 2020-01-01 00:00:00 UTC (exclusive): 1 mentions; 1 submissions, 0 comments20192020-01-01 00:00:00 UTC to 2021-01-01 00:00:00 UTC (exclusive): 2 mentions; 0 submissions, 2 comments2021-01-01 00:00:00 UTC to 2022-01-01 00:00:00 UTC (exclusive): 3 mentions; 1 submissions, 2 comments2021

Counts come from the repository’s dated source evidence. Index cutoff: 2026-11-02 08:16:59 UTC.

View mention counts and date ranges
UTC ranges include their start and exclude their end. Select a period to filter the source evidence.
PeriodStart (UTC)End (exclusive, UTC)MentionsSubmissionsComments
20172017-01-01 00:00:00 UTC2018-01-01 00:00:00 UTC101
20182018-01-01 00:00:00 UTC2019-01-01 00:00:00 UTC110
20192019-01-01 00:00:00 UTC2020-01-01 00:00:00 UTC110
20202020-01-01 00:00:00 UTC2021-01-01 00:00:00 UTC202
20212021-01-01 00:00:00 UTC2022-01-01 00:00:00 UTC312

What Hacker News says

8 sources
davidkellis·Jan 29, 2020
No. I was pretty naive in my initial attempts. I tried for many months to make Laurence Tratt's Algorithm 2 (see https://tratt.net/laurie/research/pubs/html/tratt__direct_le... ) work, but ultimately I failed. I recall running into some problem with my implementation of Tratt's idea that led me to conclude that his Algorithm 2 doesn't work as stated. My reasoning is buried in a git commit message from many months ago - I'd have to go look it up. My takeaway from Tratt's explanation was that the general technique of growing the seed bottom-up style when in left-recursion - I think I've also seen that idea termed "recursive ascent" somewhere else but I can't place it offhand - seemed reasonable, so that's what I kept working on until I figured out something that seemed to work. Later on, I ran across https://github.com/PhilippeSigaud/Pegged
Read the rest
/wiki/Left-Recursion, which describes Sergio Medeiros' technique at a high level. One of the nice things I used from the Pegged project was the unit test suite. I re-implemented some of the unit tests from Pegged in my own PEG implementation and discovered that it failed at those unit tests. It took me another number of months to figure out why my implementation failed the unit tests. I re-jiggered my implementation to make it handle the scenarios captured by those unit tests, and then naively thought "hey, it works!"... All was well until I ran across another set of unit tests in the Autumn PEG parser (see https://github.com/norswap/autumn). My implementation failed some of those as well. After another number of months, I had a fix for those too. Long long long story short, this process continued until I couldn't find any more unit tests that my implementation would fail, so once again I'm at the point where I think "well, I think it works". There have been a number of occasions where I've thought "if this doesn't work, I'm just going to re-implement Pegged in Crystal!". Perhaps that's what I should've done. Ha ha! In a few months, when I find another test case that breaks my implementation, I may just do that. We'll see. I hope it doesn't come to that. Fingers crossed. :-)
In Ask HN: What interesting problems are you working on?

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