Is opCast need, we have to!

[foobar]

Jesse Phillips Wrote:

> foobar Wrote:
> 
> 
> > > >   - 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..
> > > 
> > > This was kind of my point, to! already specifies how to generically (an important part) to other types. And opCast overrides everything (which I don't wish to claim is incorrect, just asking).
> > > 
> > 
> > I don't follow as to how this is important to have a generic interface. Can I specify parameters for conversion with to! as in my examples? 
> > I'd appreciate an example 
> 
> Oops, sorry, though I don't see why it can't be specified in to!.
> 

how would the to! usage look like with these additions? I suspect at that stage the benefits of to! genericity will be lost.

to!(int)("1010101", 2); / base 2 ? 
to!(int)(3.14, ..); // how do you specify a floor strategy here, enum? 
this quickly gets messy, ugly and redundant. 

int a = floor(3.14); // KISS - much better

> > > > 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
> > > 
> > > I think to! should be changed such that this would be a ConvException.
> > 
> > This should not even compile. a run-time exception is better than current D but is still very weak.
> 
> See my bug report, http://d.puremagic.com/issues/show_bug.cgi?id=5307
> 
> After making it a runtime error, I made it just not compile. (Error message sucks though.)

good :)
> 
> > > > 3. dynamic_cast: the language should provide a down cast operator for OO. 
> > > 
> > > Then the example above is invalid, though still valid when casting const double to int...
> > 
> > a down cast should _only_ perform dynamic down casts in the OO sense. so:
> > Base foo = new Derived; 
> > Derived bar = downCast(foo); // compiles. performed at run-time
> > 
> > [const] double -> int is not a down cast, it is a conversion.
> 
> I was referring to the need for const_cast

Sorry, I lost you here. what are you talking about here? 


>  
> > > Maybe std.math.floor should return an int, since they are implicitly converted to real...
> > > 
> > > > and also:
> > > > int x = ??; // some number
> > > > double y = x; //compile-time error
> > > > double z = double(x); // explicit
> > > 
> > > Other than overflow, which isn't fixed if made explicit, I don't see an issue with it being implicit.
> > 
> > besides the overflow issue you have mentioned, I also don't want special cases. No implicit conversions should be applied equally everywhere. 
> 
> Then be explicit in all of _your_ code. That won't stop others from using implicit conversion, but you can just assume they are of the same type and be fine.
> 

since the entire point is to prevent bugs by having compiler checks, I don't see how the above conclusion helps me at all. I want the compiler to prevent me from getting the kinds of bugs previously shown.