opDispatch() is pretty damn great

[Brad Anderson]

On Wednesday, 8 January 2014 at 23:20:06 UTC, Szymon Gatner wrote:
> Still exploring what D has to offer but this blew my mind:
>
> <snip>
>
> I don't quite understand why "enum name" part is necessary (as 
> my understanding is that "op" is compile-time constant anyway) 
> but since I am crap at D that is what worked for me. I was 
> thinking for log time how great something like that would be in 
> C++ and I just tried this id D... Mind blown... 
> std::reference_wrapper<> would be a zillion times more usable 
> with equivalent of opDispatch() this powerful.

There is also `alias this` for subtyping.

	import std.stdio;
	
	struct Base
	{
	  void print(string text)
	  {
		writeln("Base : " ~ text);
	  }
	  int add(int a, int b)
	  {
		return a + b;
	  }
	}
	
	struct Wrap
	{
	  Base base;
	  alias base this;
	}
	
	void baseOnly(Base b)
	{
		b.print("passed in a Wrap!");
	}
	
	int main(string[] argv)
	{
	  Wrap wrap;
	  wrap.print("wrapped call, magic!");
	  baseOnly(wrap);
	  auto res = wrap.add(1, 5);
	  return 0;
	}