[burlesona]

I feel like Haskell is easier to use than it is to explain, and in my experience a lot of these kind of tutorial / explanations actually make things seem harder and more complicated than just working with the concepts and observing what they do. (This one included.)

[globnomulous]

I'm not familiar with Haskell and am really, really struggling to follow the article.

In the case of the functor, the author doesn't explain in technical, specific enough terms the difference between "open the box, extract the value out of it, apply the function, and put the result back in a box" and "apply a function to a box directly; no need to perform all the steps ourselves." I have no idea what 'apply a function to a box' even means.

> That’s the essence of functors: an abstraction representing something to which we can apply a function to the value(s) inside

The error in this sentence garbles its meaning beyond recovery. "We can apply a function" governs two prepositional phrases that are semantically and syntactically identical: "to which;" "to the value(s) inside." There's no way to resolve the meaning of one without rendering the other incoherent.

[BoiledCabbage]

The number one mistake is everyone trying to explain a Haskell concept to the general population makes is using Haskell. If someone already knows Haskell there is a good chance they know there concepts. Don't use Haskell as the language, use js to explain it.

The number two mistake people make is being aware of the number one mistake so they go write yet another Monad tutorial in Javascript (or Java or whatever...). Which is why there are so many damn Monad tutorials, all saying pretty much the same thing.

[bobbylarrybobby]

The distinction is that in general “opening a box and extracting the value” makes no sense, as it's not a thing that can be done in general. If your box is a Maybe, there might not be a value to extract. If it's a list, there might be zero or multiple values. It only ever makes sense to map over the contents of the box, replacing the values with their image under the map.

[pests]

To try to answer your first question, coming form someone who is also not an expert in Haskell or monads.

"apply a function to a box directly; no need to perform all the steps ourselves."

The box doesn't change, and it also doesn't matter what's inside of it. You are attaching the function to the box, who later knows how to apply it to itself. If you were to open the box, you would need to know how to handle all the possible contents. It's key here that you are only handling a box and nothing else.

[alabastervlog]

Every “hard” concepts I’ve seen in Haskell is immediately clear to me if explained in almost any other language. The hard part is Haskell, not the concept.

Usually I’m left wondering why whatever-it-is even has a name, it’s so simple and obvious and also not that special or useful seeming, it’d never have occurred to me to name it. I guess the people giving them names are coming at them from a very different perspective.

Exception: type classes. Those are nice and do need a name.

[codebje]

Haskell has a type system that lets these things be directly useful in ways they cannot be in many other languages.

You can't, in Java, declare anything like "class Foo<F<T> extends Functor<T>>", or use a similar generic annotation on a method: you can't have an unapplied type-level function as an argument to another type-level function.

These things get a name in Haskell because they can be directly used as useful abstractions in their own right. And perhaps because Haskell remains very close to PL research.

[fellowniusmonk]

Why are there so few practical, example and code driven tutorials? I've never run across a succinct "build Twitter with Haskell" in the wild.

[jaspervdj]

This talk seems like exactly what you are looking for for:

Gabriel Gonzalez - “A bare-bones Twitter clone implemented with Haskell + Nix” @ ZuriHac 2020 https://www.youtube.com/live/Q3qjTVcU9cg

[rrgok]

Yes, I really need a real word Haskell project simple enough to understand all the math concept. Like, I don't know when to implement the Monad type-class to my domain data types. For example, taking the twitter example, if I have Tweet data type:

- should I implement the Monad, Applicative or Functor type class?

- How would that help in the big picture?

- What if I don't do it?

All these funny example of boxes, burritos or context doesn't not help me solve problems.

Take for example Monoid, I understand (partially maybe) that it useful for fold (or reduce) a list to a single value.

[ngruhn]

Highly recommend Richard Eisenbergs video series on building a Wordle solver https://youtube.com/playlist?list=PLyzwHTVJlRc9Fcinmxe97pHl_...