On Sat, 22 Feb 2014 15:17:37 -0500, Frustrated <[email protected]> wrote:
It is legal exactly because I will always guarantee that the
proper button will be used.
Static typing says it's not legal. D does not do dynamic type checking
upon calling virtual functions.
It is not logically legal as mentioned several times... no one
needs to mention that. But it is legal within the context of the
code. I'll never use a RogueButton so why force me to code for
the chance I might?
You may not be the only one using WindowsGui. You can't guarantee other
code won't do it. In any case, the compiler cannot possibly know your
intentions.
Basically, the point is, the compiler could enforce the above but
make the code more readable.
e.g.,
I do this:
@property WindowsButton button(WindowsButton b)
{
}
The compiler turns this into
@property WindowsButton button(iButton _b)
{
if (is(_b : WindowsButton)) assert(0, "Rogue button used");
auto b = cast(WindowsButton)_b;
}
This solution is not as efficient as the one I outlined. If you have a
WindowsGui object, no need to accept iButton when you require
WindowsButton.
One allows me to program in a natural way while the other makes
me jump through hoops which litters the code with a bunch of
casts and checks which are only there in the odd event that I
assign the wrong type(which, I'm not going to do on purpose).
Sorry, if you want a dynamically typed language, use one. D is not that.
Again, the whole point of why it is illegal because you can pass
a RogueButton... BUT I DON'T INTEND TO PASS THEM! If I could
absolutely guarantee that I won't pass them then there should be
no problem(no asserts). Since I can't guarantee it I have to
litter my code with checks? The compiler could do this for me.
You can't guarantee it. That is the point. The compiler could do the
checks for you, but D is not dynamically typed. The best you can do is
encapsulate the type checking code as a mixin.
-Steve
