154
class BaseFunction {
  static #allowInstantiation = false;

  constructor(...args) {
    if (!BaseFunction.#allowInstantiation) {
      throw new Error(
        "Why are you trying to use 'new'? Classes are so 2015! Use our fancy 'run' method instead!"
      );
    }
    for (const [name, validator] of this.parameters()) {
      this[name] = validator(args.shift());
    }
  }

  parameters() {
    return [];
  }

  body() {
    return undefined;
  }

  static run(...args) {
    BaseFunction.#allowInstantiation = true;
    const instance = new this(...args);
    BaseFunction.#allowInstantiation = false;
    return instance.body();
  }
}

class Add extends BaseFunction {
  parameters() {
    return [
      ["a", (x) => Number(x)],
      ["b", (x) => Number(x)],
    ];
  }

  body() {
    return this.a + this.b;
  }
}

console.log(Add.run(5, 3)); // 8



top 29 comments
sorted by: hot top controversial new old
[-] pfm@scribe.disroot.org 31 points 4 days ago

A true FP programmer would make it apply instead of run...

[-] xmunk@sh.itjust.works 11 points 4 days ago

Ahem, map...

And, of course, everything is a lazy list even if the functions can't handle more than one element in each list.

[-] bleistift2@sopuli.xyz 17 points 4 days ago

validators is a shitty name for something that actually does type conversion.

[-] BaumGeist@lemmy.ml 41 points 4 days ago

OP, what's your address? I have a "present" for you

[-] FiskFisk33@startrek.website 4 points 3 days ago

That'll be fun in a multi threaded setting!

[-] CrossbarSwitch@lemm.ee 2 points 2 days ago

I've seen something similar to this at work. Horrible.

[-] NigelFrobisher@aussie.zone 2 points 2 days ago
[-] PanArab@lemmy.ml 11 points 4 days ago

This should be programmer horror

[-] NorthWestWind@lemmy.world 20 points 4 days ago
[-] Ephera@lemmy.ml 22 points 4 days ago* (last edited 4 days ago)

Yep, some code examples from the official documentation. This:

printPersons(
    roster,
    (Person p) -> p.getGender() == Person.Sex.MALE
        && p.getAge() >= 18
        && p.getAge() <= 25
);

...is syntactic sugar for this:

interface CheckPerson {
    boolean test(Person p);
}

printPersons(
    roster,
    new CheckPerson() {
        public boolean test(Person p) {
            return p.getGender() == Person.Sex.MALE
                && p.getAge() >= 18
                && p.getAge() <= 25;
        }
    }
);

...which is syntactic sugar for this:

interface CheckPerson {
    boolean test(Person p);
}

class CheckPersonEligibleForSelectiveService implements CheckPerson {
    public boolean test(Person p) {
        return p.gender == Person.Sex.MALE &&
            p.getAge() >= 18 &&
            p.getAge() <= 25;
    }
}

printPersons(roster, new CheckPersonEligibleForSelectiveService());

The printPersons function looks like this:

public static void printPersons(List<Person> roster, CheckPerson tester) {
    for (Person p : roster) {
        if (tester.test(p)) {
            p.printPerson();
        }
    }
}

Basically, if you accept a parameter that implements an interface with only one method (CheckPerson), then your caller can provide you an object like that by using the lambda syntax from the first example.

They had to retrofit lambdas into the language, and they sure chose the one hammer that the language has.

Source: https://docs.oracle.com/javase/tutorial/java/javaOO/lambdaexpressions.html

[-] mbtrhcs@feddit.org 14 points 4 days ago

That's not quite right. In bytecode, lambdas are significantly more efficient than anonymous class instances. So while the lambda implementation is semantically equivalent, characterizing it like you have is reductive and a bit misleading.

[-] ornery_chemist@mander.xyz 5 points 4 days ago

Hence, Clojure. It's not just functions that implement IFn... as the string of "cannot cast to clojure.lang.IFn" errors that I get because I couldn't be bothered to validate my data's shape is eager to inform me.

[-] LodeMike@lemmy.today 3 points 4 days ago* (last edited 4 days ago)

Golang also does this, but it's not classes.

[-] firelizzard@programming.dev 1 points 4 days ago* (last edited 4 days ago)
[-] LodeMike@lemmy.today 1 points 4 days ago* (last edited 2 days ago)

Golang uses modules, not classes. Each of which may have its own main function.

[-] firelizzard@programming.dev 1 points 3 days ago

Huh? Main file? Do you mean main package? A module can contain an arbitrary number of main packages but I don’t see how that has anything to do with this post. Also are you saying modules are equivalent to classes? That may be the strangest take I’ve ever heard about Go.

[-] LodeMike@lemmy.today 1 points 3 days ago

I meant main function. Oops

[-] Burghler@sh.itjust.works 11 points 4 days ago

JS disgusts me

[-] TunaSlap@lemmy.world 3 points 3 days ago

What theme are you using, i like it!

[-] Chais@sh.itjust.works 4 points 3 days ago

Looks like Catppuccin Mocha

[-] TunaSlap@lemmy.world 2 points 3 days ago

Actually now that check it again its not quite right for mocha. But it's close!

[-] Chais@sh.itjust.works 2 points 3 days ago

You're right, the background is too dark. Probably crust instead of base. Maybe it was customised or created improperly.
But I'm fairly confident that the palette is Catppuccin, probably Mocha.

[-] sebastiancarlos@lemmy.sdf.org 3 points 3 days ago* (last edited 3 days ago)

I can confirm it's Catppuccin Mocha. I am not currently aware of the background color issue, but I'll look into the matter soon. Thanks for letting me know. Also how dare you. But thanks.

[-] Chais@sh.itjust.works 2 points 2 days ago

The background is most likely a color that is in the Mocha palette, just one that is intended for dark accents, not regular background.

[-] TunaSlap@lemmy.world 2 points 3 days ago
[-] navi@lemmy.tespia.org 12 points 4 days ago

Dont look at C++ with std:: function

[-] NewDark@hexbear.net 10 points 4 days ago

I'm pretty sure this post is designed to kill the soul. I am made slightly worse for witnessing this abortion of an implementation and I will never be quite the same again.

[-] Chais@sh.itjust.works 3 points 4 days ago

I think that's called a functor.

Amazing, lol

this post was submitted on 17 Nov 2024
154 points (95.3% liked)

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