Denis Koroskin wrote:
On Thu, 01 Oct 2009 20:25:03 +0400, Andrei Alexandrescu
<[email protected]> wrote:
[...]
What do you think?
Andrei
This is cool. I'd also add Serialization task to the application list
(currently I manually insert "mixin Serializable!();" into every class.
Yah, serialization is close to reflection so it's definitely part of the
target applications of the features.
There is one thing that I dislike about it, though. I believe mixin(Foo)
{} syntax is a bit far-fetched, it is not obvious that Foo represents
derived type inside a mixin scope.
I'd like to remind you that we could just use typeof(this) instead of
Foo/Derived/etc:
static if (is (typeof(this) == Counted) {
ref uint getCounter() { return counter; }
} else {
override ref uint getCounter() { return counter; }
}
Yah, I thought a lot along the likes of typeof(this). We need some
symbolic alias for "the struct or class currently being defined" and
typeof(this) is an obvious choice. I just fear that it might be
confusing that typeof(this) works even outside any method, i.e. when
there is no "this".
If you remember, we had a similar discussion about a half year ago. It
was about ICloneable interface that forces all derived class to
implement proper clone() method. We could define it as:
// forces implementor class and all the derivatives to implement proper
clone() method
interface ICloneable
{
scope mixin { // alternative syntax
typeof(this) clone();
}
}
Yah, I remember.
and also be able to declare a method non-recursively (so that derived
class don't have to implement that method):
interface ICloneableNonRecursive
{
typeof(this) clone();
}
Other possible solution could be to use a special "derived" keyword. We
already have a class-level compile-time constant - "super". We could
also introduce its counter-part ("derived"), which will expand into a
concrete derived class type. This will simplify the syntax a bit and
will allow to get rid of mixin and an addition level of indentation:
interface ICloneable
{
derived clone();
}
interface IComparable
{
int opCmp(derived other);
}
As a downside, I don't know how to define a field in every class this
way ("int derived.counter;" maybe?).
I dislike adding yet another keyword. In fact, I want to propose Walter
to eliminate "super" as a keyword and make it just an alias for the base
class as if you defined it by hand.
Andrei
