On Thursday, 31 August 2017 at 14:52:43 UTC, jmh530 wrote:
On Wednesday, 30 August 2017 at 15:59:32 UTC, Jean-Louis Leroy wrote:

What happens here is that kick(Animal) is shadowed by kick(Dog). kick(Animal) is a method but it appears to the user and the compiler as an ordinary function - which is generally good. As such it is eligible for UFCS. I would not recommend this sort of coding, but it's everyone's choice, methods or not.

Likewise, methods can be overloaded (like here https://github.com/jll63/openmethods.d/blob/1.0.0-rc.1/examples/matrix/source/matrix.d#L12).

A current limitation is that default arguments are not supported (yet), although I think it's just a matter of putting the effort in.

UFCS interacts nicely with methods because you can say a.plus(b) even if 'plus' is an open method.

I had a chance to try out what I had suggested above and it behaves exactly as I would have expected (i.e. it prints the line "lassie.kick(): ctbark").

You seemed to emphasize UFCS in your response, but that really wasn't what I was intending to focus on. I just as easily could have re-written Dog as below and compiled the program and it would have printed the same thing. Similarly, any Dog or Pitbull type that call kick would return "ctbark", just Animals would return the original results.

class Dog : Animal
    final string kick()
        return "ctbark";

My point is one can easily mix your openmethods's dynamic dispatch and D's static dispatch. That seems like a great thing that you could emphasize. Simply stated: if you use openmethods, you're not forced to only use openmethods. If you know the type at compile-time, then you can use it. It's only if you want to dynamically dispatch it that you would need openmethods.

Indeed I misunderstood.

Well, I am very pleased that my stuff interacts well with the rest of the language - I strive for that. However, I found that it is difficult to get people to open their mind to the idea of open methods, initially. Unless they come from Lisp, polymorphism and membership are almost indissociable for them. I often have to jump three hurdles.

1/ They're multi-methods, and I never actually had a use for that. That is why I insist so much on openness in the article, and throw multiple dispatch in as a bonus only half way through. That's also why I call them "open methods" and not "multi-methods" or "open multi-methods".

2/ It's just function overloading. Hmmm, polymorphism? But once I get past that, it's actually a good thing. People know (more or less) how overload resolution (or partial template specialization for the more expert) works. So I don't need to explain the rules governing dispatch and ambiguities in an abstract way. Usually I just say "you already know which override will be picked - it's the same as with compile-time overload resolution".

3/ This one is specific to D - UFCS gives me the same thing. Hmmm, polymorphism again? But you see why I am very careful with anything that may obscure or confuse the message.

I find the interaction of open methods and UFCS particularly cool when implementing the "call chain" idiom (e.g. a.plus(b).times(c).invert()).

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