Is there a way to declare classes and methods as abstract in Haxe?

Question

Is there a way in Haxe to get the equivalent of Java's abstract methods and abstract classes?

What I want is

// An abstract class.  (Written in a Java/Haxe hybrid.)
abstract class Process<A> {
    public function then<B>( f : A -> Process<B> ) : Process<B> {
        var a : A = go() ;
        return f(a) ;
    }

    abstract public function go( ) : A ;
} 

// A concrete class.
class UnitP<A> extends Process<A> {
    var _a : A ;

    public function new( a : A ) {
       _a = a ; }

    public override function go() : A { return _a ; }
}

The closest I've been able to get is to define Process as an interface and to implement it with a conceptually abstract class ProcessA, which defines both methods; the implementation of go in ProcessA simply crashes. Then I can extend my conceptually concrete classes off ProcessA.

Answer 1

As mentioned by MSGhero, Java-style abstracts are not natively supported by Haxe. It was requested by several people though, so Andy Li wrote a macro to provide Haxe users with a comparable functionality:

https://gist.github.com/andyli/5011520

Answer 2

How I'd do something equivalent in Haxe

• Set the constructor private to ensure no instance of the Abstract class is created.
• Create an Interface with all methods that must be implemented

• Create a class that inherits from the Abstract and implements the Interface.

  // An interface
  interface IProcess<A, B> {
      public function then( f : A -> AProcess<B> ) : AProcess<B>;
  
      public function go() : A;
  }
  
  // An abstract class.
  class AProcess<A, B> {
      private function new() {}
  
      public function then<B>( f : A -> AProcess<B> ) : AProcess<B> {
          var a : A = go() ;
          return f(a) ;
      }
  
      private function go() : A {};
  }
  
  // A concrete class.
  class UnitP extends AProcess<A, B> implements IProcess {
      var _a : A ;
  
      public function new( a : A ) {
         super();
          _a = a ;
      }
  
      public function go() : A { return _a ; }
  }