Staged "contains" method

gistfile1.txt

class Cons {
  final x;
  final xs;

  Cons(this.x, this.xs);

  freeze() => new Cons(((v) => <v>)(this.x), this.xs.freeze());
  contains(e) => < (~this.x).eq(~e) ? true : ~(this.xs.contains(e)) >;
}

class Nil {
  Nil();
  
  freeze() => new Nil();
  contains(e) => <false>;
}

class Demo {
  Demo();
  
  range(n) => n.eq(0) ? new Nil() : new Cons(n, this.range(n.minus(1)));
  inRange10() => run(<(e) => ~this.range(10).freeze().contains(<e>)>);
}

main() {
  print(new Demo().inRange10());
}