Le 2010-07-08 à 8:13, Andrei Alexandrescu a écrit :
> This is solid work! There's an opportunity here - it overlaps a LOT with
> std.variant.Algebraic.
Indeed. It's great. But why is the protection level set to 'package'? Isn't it
meant to be used outside of Phobos?
> Essentially it would be best if you integrated opDispatch, _onActiveDuck, and
> friends inside Algebraic. Then Algebraic would become meta-duck - it still
> supports any combination of types, but you can call any method they share
> against the Algebraic.
One thing I've missed about Algebraic is the ability to switch on the type,
somewhat like this:
Algebraic!(A, B, C) x;
switch (x.type) {
case x.typecode!A:
case x.typecode!B:
case x.typecode!C:
...
}
Seems like this would be easy by switching on Any's _duckID, but this facility
isn't exposed (it's all private).
Also, this approach using _duckID is a big difference from VariantN (and its
derivative Algebraic), which stores a pointer to the typeid to identify the
type instead of using a compile-time constant. I think the compile time
constant is better since beside being switch-friendly it makes optimizations
easier for the compiler.
So I think it'd be better to simply replace Algebraic's implementation with the
one from Any. Or perhaps Algebraic and VariantN could be retrofitted so it can
use a constant instead of a typeid pointer, but I'm not sure how it'd work.
> P.S. I *love* the trick with the homonym inner namespace! It solves the
> naming problem so elegantly. I'll use it in RefCounted too.
It's a nice trick and a good application of it.
In fact, I remember myself proposing something similar to allow properties with
overloaded operators a few months ago when the property debate was raging. :-)
--
Michel Fortin
[email protected]
http://michelf.com/
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