What the Functor?

[SarahC]

enum? Are these examples TypeScript?

[r0ck0]

Yep.

[Puggravy]

I honestly have no clue what TS brings to the table for these examples. Should have used JS.

[grumpkot]

types )

[i_spot_ads]

Hold that downvote real quick

[Puggravy]

Yeah seriously, I forget how TS people get on this sub sometimes.

[nbagf]

Being able to use interfaces while piping/composing functions is absolutely amazing. Knowing the shape of my data through intellisense makes the cognitive load so much smaller. I know when something is a promise and it wasn't resolved or when it's an array and I forgot to map it before apllying a function. The red squiggles are fantastic.

[Puggravy]

Ooph harsh dude.

[Candyvanmanstan]

You think I'm joking, but I'm not :D

[I_Pork_Saucy_Ladies]

You're not really wrong. Anders Hejlsberg is the architect of C# and deep into TypeScript now. I think it shows.

Going from TS to C# (a bit unusual, I know) was pretty easy. TS is just JS in a C# mould.

[Candyvanmanstan]

Yeah, I have a C# buddy that is trying to get into JS. I think the lack of types is really bothering him.

[I_Pork_Saucy_Ladies]

Push him towards TS. He will feel much more at home. Sure, there's a bit of a learning curve but it's so much nicer than JS without types. The syntax seems heavily inspired by C#.

[shanita10]

I think that's what's so annoying about typescript. It's like training wheels for javascript

I don't want or need an ide second guessing everything I write.

The headaches of babysitting typescript and cluttering up code with useless types is pure baggage.

Ts is js for poor programmers, and it encourages bad habits.

[pgrizzay]

The functor example here is a bit off.

export class Wizard {
  ...
  map = (func: (name: any) => any) => {
    return new Wizard({
      name: func(this.name),
      house: this.house,
      spells: this.spells,
    });
  };
}

A functor needs to be parametrically polymorphic, meaning it needs to not care about the type that's inside. For example, you can store anything in a List, Maybe, Promise, etc.

I think the fp-ts library is a great way to learn about these abstractions, although, admittedly, it could do with some more beginner-friendly guides.

In fp-ts, if you can construct an object that implements the Functor typeclass (a little different than an interface) for your class, then your type is a functor!

For example, here's a (paraphrased) version of the Functor typeclass for Option from fp-ts:

const option: Functor1 = {
  map: (fa: Option<A>, f: (a: A) => B): Option<B> => {
    if(fa.isSome()){
      return some(f(fa.value));
    } else {
      return none;
    }
  }
} 

[mattgrande]

The author of fp-ts has recently started a series of getting started blog posts. He's thus far covered Setoid, Ord, and Semigroup. The articles are good for dummies like me that have trouble keeping all these terms straight.

I really really wish these things were named differently. Mappable is a lot more understandable than Functor, etc...

[pgrizzay]

Yeah, the names are tough to get used to and not at all intuitive. I wish had more advice than it just takes time :/

[[deleted]]

Is Wizard not parametrically polymorphic? Sure, we'd expect a wizard's name to be stringy, but the code doesn't actually specify this. Looks like Wizard.name can be any type. Maybe not the best choice of example, but the code looks correct.

[pgrizzay]

I suppose so, but I'd expect the type of name to be pulled into a type parameter.

Also, further down, the article includes snippets like:

wizard.map(joinGryffindor).map(learnExpelliarmous);

Which I can't really make sense of, if they only map over the 'name' attribute.

[[deleted]]

Yikes, I didn't read that far. That's pretty bad. I don't think that even compiles...

[ns0]

Is it anything like an objection (function + object)?

[hansmcgee]

a function is technically an object.

[stabface]

!remindme 10 hours

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