quartz.qz

func identity<A>(x: A): A {
  x
}

enum List<A> {
  Nil,
  Cons(A, List<A>),
}

record User {
  user_id: string,
  age: int,
}

instance List<A> {
  open List.*;

  func length(self): int {
    case self {
      Nil -> 0,
      Cons(x, xs) -> 1 + xs.length(),
    }
  }

  func concat(self, other: List<A>): List<A> {
    case other {
      Nil -> self,
      Cons(x, xs) -> self.snoc(x).concat(other)
    }
  }
}

func public_length(xs: List<A>): int {
  ...
}

func main() {
  let xs = {
    open List::*;

    Cons(
      1,
      Cons(
        2,
        Nil
      )
    )
  };

  println("{:?}", xs.length());
  println("{:?}", List.length(xs));
}