On Fri, 19 Nov 2010 16:48:50 -0500, Michal Minich
<[email protected]> wrote:
On Fri, 19 Nov 2010 21:37:45 +0000, div0 wrote:
On 19/11/2010 21:22, Jonathan M Davis wrote: At runtime, the runtime
type info for classes forms a DAG.
As D only allows single inheritance it should be trivial to find the
most derived class, though the runtime doesn't currently offer a
function for this.
Just because an object is able to know what its actual type is - or
even its base classes - does not mean that you could ask it what other
types exist which are derived from one of its base types or its exact
type. Sure, D definitely _could_ provide the necessary type information
at runtime (C# and Java do that sort of thing - which is why thy can
have runtime reflection), but it doesn't. At best, you can get
information on the types of a particular object from that object, not
the types which exist in general.
- Jonathan M Davis
So just ignore the bit about dynamic cast completely then and repeat
your first incorrect assertion.
Yes D and C++ do provide a limited amout of runtime type information.
It's called RTTI surprisingly enough. *cough*
Dynamic cast, *explicitly* asks at *runtime* if some base class can be
converted to a *more derived* class.
You *can not* do that unless base classes know about the classes which
*inherit from* them.
In current dmd, when you make a cast like: cast (Derived) base, you
explicitly mentioning the *Derived* type. Its typeinfo contains info
about classes it derives from, so it the cast just check if type of
"base" is one of them.
Given two types, you can determine if they are related at compile-time.
Derived classes contain pointers to their base class' classinfo.
Compiler currently does not push informations from Derived classes to
base class type info, so it is not possible currently to find out what I
wanted.
Not at compile time. The runtime contains all the classinfos, so you can
iterate them all and find ones that derive from your base.
-Steve
