I started learning programming in the imperative style with Python and Javascript. After learning Rust and then recently basic Haskell, my mind was opened to how functions are all you need (according to lambda calculus). But what I also took from Rust and Haskell is that algebraic data types are all you need: just like using "and" and "or" allows you to state so many combinations of phrases in English, product and sum types cover so much of the spectrum. But functions are like implications in English: "if I have A then I have B". They're like pseudo-values where they will have a definite value but only when applied with the required argument. That allows you to work backwards by parameterizing the multiple variants (aka "or" sums) in your output type according to various "or" sum variants in the input domain. So defunctionalization is expressing the sum variation as values rather than function pseudo-values. And that means you can serialize them for storage and transfer compared to true functions. It probably also is important for designing compatibility layers because a C function and Ruby function may not be the same but if they can be serialized to equivalent sum types, then they should be compatible.

10:00 This all makes me think about tensors and the ability to talk about covariance and contravariance at the same time explicitly: for example, a vector is a (1,0)-tensor, a covector/linear form is a (0,1)-tensor, a linear vector space map is a (1,1)-tensor, etc. It seems that (co-)functors are either fully covariant or contravariant but never mixed. What would be a category theory / type theory / functional programming equivalent of a mixed tensor which could have some number of covariant and contravariant pieces? Edit: It seems he explained something like a (1,1)-tensor from abstract algebra as a Profunctor in that it takes 1 contravariant input type and gives 1 covariant output type. But I'm wondering about the terminology that generalizes (p,q) tensors so that you could talk about something that takes 42 contra- input types and gives 314 covariant output types.

Really a good idea, wonder few people watch

I have enjoyed going back to look at some of these concepts. Thank you for your presentation. Being a low vision individual, SEEING what you are speaking of is almost impossible unless it is on a black or dark blue background. Fortunately, you were very clear in speaking about what appeared on the screen. Thank you. Please consider us "low vision folk" in the future? <3 💘

nice

amazing

Don't quote me on this, but regarding the "open vs. closed" tradeoff, I think the issue relates closely to the expression problem - therefore, we could use a solution to that in order to recover the openness. Again, don't quote me, but I think this could be achieved (in Haskell, at least) using a typeclass with an associated data type. That way you can create instances of the class "SerializableFn" where you must provide a Data type for each instance and a mapping function to/from said data type cases to the appropriate function/s relevant to that instance. That way - whilst you still need to update the code to handle the new case of course - any old code that just uses the typeclass will have the changes propagated automatically; the same way the definition of (+) itself doesn't need to be modified for each new instance of Num a. Not sure whether this would be able to work out with the kinds, or regarding (multiple) type variables, but it seems somewhat promising. I have a feeling the Haskell MemoTrie library and associated paper "Memo Functions, Polytypically!" may bear some relation.

Great speaker and great talk!

Is Maybe a special case of Either Nothing?

For everyone who is suffering because of the audio: Easyeffects with noise reduction and autogain makes it sound pretty ok :)

wow good talk!

Please, ask some help from an audio technician!

Great video. Please keep making more of them George.

Donya? or Sonya? Is that a typo too?

I finally understood monads. Thanks Dr Riehl!

good

Nat <: nat , so how influenced is this from Russell's type theory? Also you can't derive subsumption rule when row type instantiated Jury is still out on, if 0 is nat

KDA will be legendary.. amazing technology

9:04 you can in C++ :3

Ptghci is also quite good for a terminal REPL

Here we go boys

this is a crazy way to produce music.... i am wondering how this sounds? ;-)

Can this analyze the program Ken Griffin uses to manipulate the fraud market?

"Lock-step simulation is child's play" Me: This must be the reason I can't do it because I'm not a child anymore 😥

Even in 2022 great talk. Well done

I just want to say this technique is obnoxious. Pretty much the whole point of the this technique would be to apply it to the task of iteratively walking through a tree structure and accumulating a value from it. When this gets brought up on the internet, its always (like this video) walking through a tree structure and NOT accumulating a value or, like other articles, accumulating a value from a sequence structure (like summing a list). Table stakes for this technique to be useful is walking a tree AND accumulating a value - but once you do that, the method shown here just doesn't work - why? because you have 2 different conceptual stacks to maintain (one to maintain position in the tree and one to accumulate the value) and the inlining no longer works the same way and there is just nothing out there that bridges the gap.

12:41 프로세스

I watched this talk for the first time around when it was delivered, when I was first properly getting into FP. Even given that, I've watched it at least three times in the past three months. It's just so fun.

Bret Victor reference detected.

\m/..\m/

thank you sir ❤️

Wonderful presentation. Thank you.

Excellent talk. Terrible audio. But excellent talk.

22:11 live coding begins

Kadena ✅🔥

Great talk and props for the King Chrimson shirt :)

Great talk even in 2021!

'I have to get back to Science...' <3 the music was cool af tho the code could watch out for timing 'errors' in the human's playing too perhaps to derive micro timings?

We need more of them

23:52 Lmao, George Wilson is there! 😂

You are amazing!

Amazing talk

Great name!

What font does he use?

great work

i'm really glad I stumbled upon this talk. Thanks

i like how he says DO DO

Thank You for this wonderful talk! Very helpful! :) that explain of map and fmap at 1:20 is very very comprehnsible, cool!

I am very intrigued. I would like to learn more!

The person dying of consumption in the audience with their phlegmy coughs is really distracting, but the talk is fantastic.