https://github.com/bitemyapp/learnhaskell/blob/master/dialog...
> a transducer is recognizing that the signature of foldl splits
> type Transducer a b = forall r. (r -> b -> r) -> (r -> a -> r)
> they compose like lenses
In Ask HN: What piece of code/codebase blew your mind when you saw it?bitemyapp
learnhaskell
Makefile2014–2022
bitemyapp / learnhaskell
learnhaskell
Learn Haskell
33Distinct people
64Mentions
2Explicit recommenders
8KGitHub stars
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What it is
Learn Haskell
GitHub
Where it is used
No documented product use was verified in the last source check.
What people are saying
I recommend this, https://github.com/bitemyapp/learnhaskell
lockfinn used a recommendation phrase. 2 indexed comments match. This is a phrase match, not a verdict.
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Also in these discussions
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This week on Hacker News
Nov 7–Nov 14 UTC · Direct repository links and separately labeled related project stories. Indexed through 11/14/2026, 12:54:37 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 year64 dated mentions
Observed mentions: 2014-05-20 11:05:25 UTC to 2022-11-01 06:32:14 UTC.
Counts come from the repository’s dated source evidence. Index cutoff: 2026-11-02 08:16:59 UTC.
View mention counts and date ranges
| Period | Start (UTC) | End (exclusive, UTC) | Mentions | Submissions | Comments |
|---|---|---|---|---|---|
| 2014 | 2014-01-01 00:00:00 UTC | 2015-01-01 00:00:00 UTC | 23 | 1 | 22 |
| 2015 | 2015-01-01 00:00:00 UTC | 2016-01-01 00:00:00 UTC | 25 | 1 | 24 |
| 2016 | 2016-01-01 00:00:00 UTC | 2017-01-01 00:00:00 UTC | 7 | 0 | 7 |
| 2017 | 2017-01-01 00:00:00 UTC | 2018-01-01 00:00:00 UTC | 2 | 0 | 2 |
| 2018 | 2018-01-01 00:00:00 UTC | 2019-01-01 00:00:00 UTC | 1 | 0 | 1 |
| 2019 | 2019-01-01 00:00:00 UTC | 2020-01-01 00:00:00 UTC | 2 | 0 | 2 |
| 2020 | 2020-01-01 00:00:00 UTC | 2021-01-01 00:00:00 UTC | 0 | 0 | 0 |
| 2021 | 2021-01-01 00:00:00 UTC | 2022-01-01 00:00:00 UTC | 1 | 0 | 1 |
| 2022 | 2022-01-01 00:00:00 UTC | 2023-01-01 00:00:00 UTC | 3 | 0 | 3 |
From the project README
An excerpt from the repository, fetched Nov 13, 2026.
Read the project’s introduction
How to learn Haskell
This is a recommended path for learning Haskell based on experience helping others. A list of recommendations from one of the authors of the Haskell Book.
For non-English speakers
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Don't sweat the stuff you don't understand immediately. Keep moving!
Community
Our IRC channel is #haskell-beginners on Libera Chat.
IRC web client here.
The haskell mailing lists.
Community Guidelines
See the community guidelines to understand the conduct that is expected in the IRC channel. You'll get a warning if you're not obviously trolling, but be aware the channel is exclusively for those learning or teaching Haskell.
Installing Haskell
Use Stack to get going with Haskell
Get Stack to get GHC installed and to build your projects.
If you don't know anything about Stack and would like an overview, check out this comprehensive Stack video tutorial.
Also, DO NOT INSTALL HASKELL PLATFORM
Instead of following the instructions on Haskell.org, get Stack.
Why not platform?
https://mail.haskell.org/pipermail/haskell-community/2015-September/000014.html
How should I learn Haskell?
The core recommendation is to read the lectures and complete all exercises/homework for the Spring 13 version of cis1940 followed by the FP course. Both are linked below. Everything else can be considered optional and is mentioned so you know where to look.
Haskell Programming from First Principles.
@dmvianna wanted me to let you know that the below are just the free recommended resources. If you're willing to check out a book, we heartily recommend our own Haskell Book! If you can't afford the book for any reasons, please email us using the contact information at our support page.
Haskell Book subsumes all of the primary resources recommended here
Yorgey's cis1940 course
Do this first if aren't getting the Haskell Book, this is the best free introduction to Haskell.
Available online.
Brent Yorgey's course is the best I've found so
far. This course is valuable as it will not only equip you to write basic
Haskell but also help you to understand parser combinators.
The only reason you shouldn't start with cis1940 is if you are not a programmer
or are an inexperienced one. If that's the case, start with
Thompson's book and transition
to cis1940.
Functional Programming course
This is the course we recommend doing after Yorgey's cis1940 course
Available on github here.
This will reinforce and give you experience directly implementing the
abstractions introduced in cis1940, this is practice which is critical to
becoming comfortable with everyday uses of Functor/Applicative/Monad/etc. in
Haskell. Doing cis1940 and then the FP course represents the core
recommendation of my guide and is how we teach everyone Haskell.
Supplementary course after cis1940 and the FP course
Provides more material on intermediate topics
cs240h is available online:
Spring 14
Winter 16
This is Bryan O'Sullivan's online course from the
class he teaches at Stanford. If you don't know who he is, take a gander at half
the libraries any Haskell application ends up needing and his name is on it. Of
particular note if you've already done the Yorgey course are the modules on
phantom types, information flow control, language extensions, concurrency,
pipes, and lenses.
Resources for specific topics in Haskell
These resources are not vetted or tested with learners as cis1940 and FP course have been, but they're linked in the topic listing so you have ideas on where to begin. This includes things like intermediate/advanced concepts and subjects like tooling and text editors.
Dialogues
Hosted in this repository here.
These are actually pretty important and helpful. Look here for deep dives on a
variety of topics.
Read the full README on GitHubWhat Hacker News says
64 sourcesThe author maintains an opinionated path to learning Haskell[0], albeit lacking the criticism of resources that ultimately do not make it into his final recommendation.
[0] https://github.com/bitemyapp/learnhaskell
In Functional Education (2014)I find the following type signature captures the essence:
type Transducer x y = forall b. (b -> y -> b) -> (b -> x -> b)
https://github.com/bitemyapp/learnhaskell/blob/master/dialog...
In Understanding TransducersI went through most of the Hutton book but I already had an elementary background in the language. Then some of the recommended CIS194 course. (3-6 months spent studying total.) Finally I decided upon a project that was right in one of Haskell's strong points: parsing/compilation [0]. Everything was a Google search: how to start a Haskell project with Nix? How parse command-line arguments? How to write a parser for a calculator? What the hell does this compiler error mean??!! Find the answer and get straight back to it. I would still consider myself intermediate, and not proficient, at the language.
While it is one person's opinion (albeit well explained) I strongly appreciated Chris Allen's efforts to evaluate existing learning material (prior to co-writing his book) as well as recommending a learning path [2]. Ultimately there is multit
Read the rest
udinous material to study. For the textbook-like route, choose something that seems sensible and commit, leaving only when it appears to no longer be fulfilling the purpose. Juggling too many artifacts is like interrupting programmers.
I don't use VS Code but again, my elementary knowledge of the language, plus sufficiency with GHCi, meant I could stay within my Vim comfort zone. If anyone has a good single resource for configuring Vim for Haskell I'd love to see it?
[0] State of the Haskell ecosystem https://github.com/Gabriel439/post-rfc/blob/master/sotu.md
[1] Functional Education https://bitemyapp.com/blog/functional-education/ (December 2014)
[2] How to learn Haskell https://github.com/bitemyapp/learnhaskell
The canonical source for Haskell introductions is the following, I believe
https://github.com/bitemyapp/learnhaskell
In Learning Haskell is no harder than learning any other programming languageThis is the canonical resource, I believe
https://github.com/bitemyapp/learnhaskell
In Learning Haskell is no harder than learning any other programming languageChris Allen, one of the authors of HaskellBook.com, has a list of recommended (free) learning resources:
https://github.com/bitemyapp/learnhaskell/blob/master/README...
In Ask HN: Best resource for learning Haskell?I'm learning myself some Haskell (so I'm far from an expert, so take this with a grain of salt...), but AFAIK the current recommended introductory resources are described here: https://github.com/bitemyapp/learnhaskell
tl;dr: 1) If you want to buy a book, http://haskellbook.com/ is supposed to be good
2) If you instead want to learn from free online sources, a) cis194 spring 2013 followed by b) The data61 course (links in the github link above).
In Why I’m Learning Perl 6Take a look at this link from Chris Allen (aka bitemyapp): https://github.com/bitemyapp/learnhaskell
The current best resource for beginning with Haskell seems to be haskell-book (listed on the Github link above): http://haskellbook.com/. Chris Allen also authored this book with Julie Moronuki.
If you're looking to diversify your interests to broader CS/FP topics, you may find this link helpful: http://reinh.com/notes/posts/2014-07-25-recommended-reading-...
Other references from around here: https://news.ycombinator.com/item?id=9807066
In Ask HN: Best Book to Learn Haskell And/or Functional Programming Paradigms?Some links that might be of interest:
http://bitemyapp.com/posts/2014-12-31-functional-education.h...
http://bitemyapp.com/posts/2015-08-23-why-we-dont-chuck-read...
http://bitemyapp.com/posts/2016-02-06-haskell-is-not-trivial...
https://github.com/bitemyapp/learnhaskell
http://haskellbook.com/ by the above author
In Exploratory Haskell (2015)I think Chris Allen nailed the Haskell-learning path:
https://github.com/bitemyapp/learnhaskell
or, http://haskellbook.com/
In A Haskell Study Syllabus>and perhaps fully grokking these essential constructs before moving on to using them indirectly through all the layers of pretty syntax would have helped me understand all those features better.
This is the approach we take in our book, Haskell Programming from First Principles. (http://haskellbook.com/) The book starts with a _brief_ introduction to lambda calculus and builds on what the reader knows incrementally. You can see in our chapter listing: http://haskellbook.com/progress.html what order we do things in. Importantly, it's not just show & tell. The book has _a lot_ of exercises and detailed explanation for the concepts covered.
I'd worked with and taught quite a few people before starting the book, in addition to maintaining a fairly popular guide (https://github.com/bitemyapp/learnhaskell) for learning Haskell and helping peop
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le working through the recommended materials. Further, my coauthor on the book was completely new to programming when she began working with me. What we cover and in how much detail is influenced by working with her, our ~10 deep-dive reviewers, and the over 1,300 emails of feedback/questions we've gotten from readers.
What I did in the book is based on that experience and data. If I could've written less and still solved the same problems, I would've. Maybe a future edition will be shorter after we refactor some things.
>By the time I reach cardinality I wonder if maybe the author is more interested in making things sound intimidating than helping?
I'm overstating my case in that post, but underestimating how hard this currently is doesn't change that there are things you'd want to understand before diving into a Haskell web application. Part of this is on the framework designers, it's mostly/only Scotty that has made any attempt not to incorporate concepts that would be difficult for beginners and it's more "hiding" than "not using".
You don't need 100% grokhood all along the way, but the current status quo is that people frequently flounder and burn out because the resources they _did_ use didn't explain things usefully or cover enough. This is not conjecture, this from a _lot_ of time spent working with people hands on via IRC and Skype and curating a
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popular guide: https://github.com/bitemyapp/learnhaskell
>"Why can’t I learn Haskell the way I learned $BOZOLANG?"
>...I hope the book itself won't encourage the stereotypes about Haskell the way this post does.
The stereotype that I grew up reading c2 wiki and hacker lore? I've spent most of my career so far writing C#, VB.NET, and Python. I don't even really mind a bit of Python here and there, but I don't have much cause to resort to it any more except for Ansible.
As it stands, our readers have been taking breaks from the book to successfully work on side projects starting at about chapter 9 through chapter 26. Different people find there are different spots in the book where they can step away and get things done. The point is that the rest of it is always there if they need it. Education-by-blog-diaspora has not been terribly successful for many Haskell beginners up to this point. Partly because there aren't enough people for there to be enough angles on something that beginners can reliably find something that "clicks" for them. Another problem is that you want exercises to thoroughly understand a different way of thinking about and putting together programs.
In the end, it feels little different in my head than when I'm writing in something imperative, but the experience is more difficult than it needed to be for beginners for a long time. The book is me "scaling up" my ability to help people. Like it or don't, whatever, but please don't try to make a blog post I wrote into something it isn't so you can try to take me down ad hominem.
>...I hope the book itself won't take this tone. The community doesn't need it.
You can find out what the tone of the book is by checking out the sample provided on the book's website. No need to speculate. As it is, the tone is light but to the point. Readers have enjoyed the dry humor which is not at all like how I write on my blog. Which people have liked too. You should spend less time on HN commenting on things you don't like.
I have writing to do. Goodnight.
Hi, I'm a co-author of the book mentioned. Unpublished might be a bit uncharitable, the current version of the book is 26 chapters and over one thousand pages.
As for why? We make certain you actually learn everything you need to know and we _aggressively_ test and review the material with actual learners. My co-author Julie's first programming language is Haskell, which she has learned from me and while writing the book.
Here's a screenshot from our Zendesk for processing reader feedback and reviews: http://imgur.com/EdpL4ql
We are writing the book because I've been helping people in IRC (#haskell-beginners mostly which floats around 300 users), on Twitter, etc. I saw too many people burn out and give up with the existing resources (free & paid), despite maintaining a guide for learning Haskell with free resources: https://github.com/bit
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emyapp/learnhaskell
It's just harder than it needs to be, so we're fixing that. Even the better existing books/resources don't cover nearly enough for somebody to move on to, say, writing a web application.
I wrote about the pedagogical issues with some of the existing resources here: http://bitemyapp.com/posts/2014-12-31-functional-education.h...
If you didn't find it difficult to learn Haskell, that's great! But most people find it intensely difficult and I think that's completely unnecessary. I've given a talk on this titled, "Learn Haskell in less than five years" located here: https://www.youtube.com/watch?v=Bg9ccYzMbxc
There's only one way to learn Haskell: you have to use it!
Both links below show how friendly the Haskell community is for people willing to learn:
https://github.com/NICTA/course/blob/master/README.markdown
https://github.com/bitemyapp/learnhaskell/blob/master/README...
Good luck on your journey!
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