Re: opDispatch() is pretty damn great

[Szymon Gatner]

On Wednesday, 8 January 2014 at 23:27:37 UTC, Brad Anderson wrote:
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;
        }

I was actually thinking about subtyping too but I don't know how 
to do alias this with opDispatch() call forwarding to Base from 
Wrap