duck!

[Andrei Alexandrescu]

On 10/17/2010 01:54 AM, lurker wrote:
> Andrei Alexandrescu Wrote:
>
>> I was talking to Walter about Kenji's adaptTo. We both think it's a
>> very powerful enabler, but adaptTo is a bland name. After
>> discussing a few marketing strategies, I proposed "duck". It's
>> short, simple, and evokes "duck typing".
>>
>> class C { int draw(){ return 10; } } interface Drawable { long
>> draw(); } ... auto c = new C; auto d = duck!Drawable(c);
>
> Object c = new C; auto d = duck!Drawable(c); // awes
>
> does this work? After all, c is a C:
>
> Object c = new C; auto d = duck!Drawable(cast(C)c);
>
> One fears this feature has little real world use. But it's a great
> way to add additional bloat to the puny little Phobos...
>
> It's amusing as always that the syntax is being discussed before we
> even know how this works. How does the int ->  long coercion work
> there? Any possibility to get a written spec for this?

Fair point, but the discussion started as simply naming a 
well-understood artifact. That was Kenji Hara's code here:

http://github.com/9rnsr/scrap/blob/master/interfaces/interfaces.d

Essentially what his function did was to offer a given interface on top 
of an object (that did not implement the interface). The mechanism for 
doing so was to generate simple forwarding functions.

 From there, the discussion sprawled into defining different similar 
functions, i.e. one that implements a given interface for a given object 
on a best-effort basis and throws for non-matched methods.

Discussion also extended into a completely dynamic facility that 
promises any method and uses runtime reflection (and exceptions) to 
implement dynamic typing. It has been rightly pointed out that Variant 
is the best type for that.

Once such functions will be integrated into Phobos, they will be 
properly documented. I think it's okay to keep the discussion loosely 
structured for now.


Andrei