Well, the @haskell_foundation has elected an outspoken transphobic, homophobic accelerationist to its board. That's a good thing that they avoid 'touchy topics' though. https://discourse.haskell.org/t/controversy-surrounding-anduril-industries/10253/68

Controversy surrounding Anduril Industries

Ok well, that’s awful that the Haskell Foundation would elect an outspoken transphobic, homophobic accelerationist. Do you not consider these to be ‘touchy topics’, @LaurentRDC ?

discourse.haskell.org

We can now reverse scans simply by applying the Backward applicative. We can still implement Arrow: composition is given by the Compose applicative, (***) is obtained by the Day applicative. Voilà! No more zips!

The foldl hackage.haskell.org/package/foldl package is one of the most remarkable bit of the Haskell ecosystem. Turns out, we can make it better. I mean worse. I mean… maybe?

kind of funny way to use a trees-that-grow style GADT pattern is to have terms for natural deduction where you can select whether to do minimal | intuitionistic | classical logic

Released proarrow-0.4.0.0! Lots of small changes, and 2 new examples: a clocked digital circuit and a parallel build scheduler. The wiki explains what's going on: github.com/sjoerdvissch...

I haven't mentioned the embedded language for monoidal categories in proarrow yet! It is modular: only if you copy or discard a variable it requires a comonoid on the type, and similar for traces, duals, exponentials etc. Read more here: github.com/sjoerdvissch... #haskell #categorytheory

I haven't mentioned the embedded language for monoidal categories in proarrow yet! It is modular: only if you copy or discard a variable it requires a comonoid on the type, and similar for traces, duals, exponentials etc. Read more here: github.com/sjoerdvissch... #haskell #categorytheory

proarrow 0.3.0.0 is now released with this feature. #haskell #categorytheory

Sjoerd Visscher@sjoerdvisscher.w3future.com · 4w ago

`einsum @"kl,jkk,ijx,li->li" v u t w` becomes:

Applied category theory at work: proarrow now comes with a well-typed einsum implementation, optimized through open hypergraphs. The same spec runs in any hypergraph category (matrices, relations, string diagrams), and with a bit of tensor-network plumbing it keeps up with numpy.

proarrow-0.1.0.0 is now live on hackage! hackage-content.haskell.org/package/proa... #haskell #categorytheory

Sjoerd Visscher@sjoerdvisscher.w3future.com · last mo.

If you have laws-as-code and you have code-as-diagrams, you get (you guessed it) laws-as-diagrams for free! github.com/sjoerdvissch...

If you have laws-as-code and you have code-as-diagrams, you get (you guessed it) laws-as-diagrams for free! github.com/sjoerdvissch...

If you have laws-as-code and you have code-as-diagrams, you get (you guessed it) laws-as-diagrams for free! github.com/sjoerdvissch...

playground.terrorjack.workers.dev weekend toy project: haskell playground based on ghc-10.0, with multi-file editor, ghci repl and haskell language server; transitive deps of hls like aeson are also included. note that this is a vibe coded poc, if you have allergies to this kind of thing

Apologies for the AI use, but I wanted to explore this in Oleg's visual style. Probably a lot of errors - I know spent too much time trying to get this even to this point. Script to generate it: gist.github.com/thomasmarsh/...

This is getting complicated! #haskell #categorytheory

That is, for any object A, we have an arrow α_A : F A -> G A, such that for all R∈Rel(A,B), F(R) ⊆ G(R(α,α)) If F is a functor, parametric arrows should be natural, for instance. This should give us an algebraic framework to talk about what we've been doing in PLT. 6/7

New optics just dropped! #haskell #category-theory

I’ve been working on proarrow for 3 years and only now I find out that all adjunctions between profunctors are trivial, as in they are always adjunctions between the two representables induced by a functor. At least it’s true for Hask enriched profunctors. Something to do with Cauchy completeness.

In today’s episode, we’re joined by Brent Yorgey, Associate Professor of CS at Hendrix College and the creator of the Diagrams vector graphics library and Swarm, a 2D programming and resource gathering game. We talk about teaching, DSLs, and competitive coding. haskell.foundation/podcast/85/

Dutch has this word "al", which frequently starts a sentence, and then it looks like "Al", indistinguishable from "AI" in most fonts, really annoying!

Cool observation: one can build a bicategory whose objects are free word monoids over alphabets and whose morphisms are Turing transducers. A Turing machine then appears as a specialization of a guarded trace between a Moore machine (tape) and a Mealy machine (controller).

Looking for non-trivial examples of virtual double categories arising in TCS or logic, ideally many-object examples where the virtuality has a concrete computational/logical meaning.

Using AI to write your code is like hiring a consultant to write your code, but continuously hiring a different one. No matter how good you set it up, documenting everything etc., over time the result is terrible.

after two years of development, I finally demoed Jermaine for the first time - a language with fully symmetric data and codata, and native call-cc.

I never thought the proarrow library would grow this big. I expected to hit a major roadblock at some point but that just didn't happen. sjoerdvisscher.github.io/proarrow/ #haskell

I want to explain what's going on here. Because it's quite interesting. The type of monads over the category of presheaves is given by class PMonad f where return :: p i -> f i (>>=) :: f p i -> (forall j. p j -> f q j) -> f q i (just follow the textbooks) 1/11

Conor Titania Mc Bride@pigworker.bsky.social · 4mo ago

I told a tall story about type inference via effects and handlers, this morning in Bristol. Thanks to my lovely hosts! www.youtube.com/watch?v=Vc2n...

What an amazing hack! This is a trick that works for any category, reifying any morphisms you have available into dictionaries, and then letting the compiler compose them together automatically to get the right morphism you need! #haskell

Conor Titania Mc Bride@pigworker.bsky.social · 4mo ago

I told a tall story about type inference via effects and handlers, this morning in Bristol. Thanks to my lovely hosts! www.youtube.com/watch?v=Vc2n...

I have an elasticube wooden puzzle at home, and yesterday I saw a version in a museumshop with balls instead of cubes. This allows for different shapes to be made, but the smooth surface of the balls caused the shapes to lack stiffness.

Pre-registration for this year's ICFP programming contest is open! You may register your team at your leisure at icfpcontest2026.com/signup The contest begins on July 24th - just under two weeks to go!

Are you also annoyed that the Bluesky Haskell feed is full of hurricane warnings for the town of Haskell? I just found this alternative feed: bsky.app/profile/did:...