Mappable.hx

interface Mappable<M, A> {
   public function map<B>(f:A->B):Of<M,B>;
}

class MyArray<A> implements Mappable<MyArray<In>, A> {
   var a:Array<A>;
   public function new () {
     this.a = [];
   }
   public function map<B>(f:A->B):MyArray<B> {
      var r = new MyArray();
      r.a = a.map(f);
      return r;
   }
}

class MyList<A> implements Mappable<MyList<In>, A> 
{
   var a:List<A>;
   public function new () {
     this.a = new List();
   }
   public function map<B>(f:A->B):MyList<B> {
      var r = new MyList();
      r.a = a.map(f);
      return r;
   }
}

class Main {
  // abstract over the type constructor
  public static function withMappable <M>(m:Mappable<M, Int>):Of<M,Int> {  
    return m.map(function (x) return x + 1);
  }

  public static function main () {
     trace(withMappable(new MyArray()));
     trace(withMappable(new MyList()));
  }

}