Is opCast need, we have to!

[foobar]

Jonathan M Davis Wrote:

> On Wednesday, December 01, 2010 14:32:12 bearophile wrote:
> > foobar:
> > > 1. static_cast:
> > >   a. Remove ALL implicit coercions inherited from c such as double ->
> > >   int, b. I don't see the need for an operator for conversions since
> > >   they can have different parameters, e.g.: - converting to string can
> > >   have formatting specified
> > >   - converting string to numeric types with optional base parameter
> > >   - converting integer to floating point specifies
> > >   round/floor/ceiling/etc..
> > > 
> > > 2. const_cast: should be a _separate_ operator in order to prevent
> > > removing const by mistake.
> > > 
> > >   const Base obj1 = new Derived();
> > >   auto obj2 = cast(Derived)(obj1); // oops: meant to only down cast
> > > 
> > > 3. dynamic_cast: the language should provide a down cast operator for OO.
> > > 4. reinterpret_cast: unsafe and should be restricted as much as possible
> > > (Not available in @safe code) maybe not provide it at all since it's
> > > implementable via union. A restricted library solution for when you
> > > really want to play with bits and bytes?
> > 
> > There are some ideas here, like the separation from const_cast, dynamic
> > cast, and other casts. In past I too have asked for something similar, but
> > I think Walter was not interested.
> > 
> > I guess the idea of having a single cast is to keep the language simple.
> > But those _are_ different kinds of casts, they have different semantics.
> > Lumping different semantics into the same syntax is not a good way to
> > simplify a language, in my opinion. It just creates obscurity and maybe
> > some other troubles too.
> 
> And how many programmers do you know who actually, really know the differences 
> between the 4 C++ cast types. _I_'m not sure that _I_ know, and I've studied it. 
> And honestly, in most cases - if not in _all_ cases - as far as I can tell, the 
> compiler should be able to determine the correct cast type. So, forcing that on 
> the programmer is just stupid. If you actually _need_ separate cast types, then 
> we should have them, but if we can avoid that, we definitely should. I think that 
> the fact that C++ has so many types of casts is horrible. I try and use them 
> correctly, but I don't think that there are very many programmers (percentage-
> wise at least) who do. I know plenty of programmers who just use C-style casts 
> everywhere.
> 
> - Jonathan M Davis

My suggestion is much simpler than c++. 
the _language_ needs only to provide two operators: 
down cast operator and const cast operator. 
interpret cast is a corner case that can also be implemented as a library utility. 
conversions can and should be done with regular D code (functions). which is not far from current D idioms (to!).