Convert TickDuration to Duration?

[Jonathan M Davis]

On 2011-06-09 10:58, Steven Schveighoffer wrote:
> On Thu, 09 Jun 2011 13:33:28 -0400, Jonathan M Davis <jmdavisProg at gmx.com>
> 
> wrote:
> >> On 09.06.2011 16:33, Steven Schveighoffer wrote:
> >> > Hm... this involves cast(Duration)x? That seems like a dangerous thing
> >> > for a common operation, no?
> > 
> > There's nothing dangerous about it. It's an overloaded opCast, not a
> > built-in
> > cast. Now, there was some talk of figuring out how to set it up so that
> > you
> > could define in your type how to use the to function to convert instead,
> > and
> > that would be better (though I have no idea what the situation with that
> > is or
> > what's involved in that), but an overloaded opCast is the same as a
> > normal
> > function except for its calling syntax, so it's perfectly safe.
> 
> What I mean is, whenever you use the blunt instrument 'cast' anything can
> happen. This code:
> 
> cast(x)y;
> 
> can do a lot of damage, depending on what x and y are. IIRC, you recently
> said that one should avoid use casting if you can help it :)
> 
> It doesn't matter if the underlying cast is safe, the keyword cast means
> "do whatever I say". It doesn't mean "do whatever I say but only if it's
> an opCast operation". One slight misstep, and the compiler will silently
> obey instead of giving you an error. We've been told numerous times "if
> you want to find all the places where your code bypasses the type system,
> search for the word cast".
> 
> My point is, why can't this function simply be a function (like
> toDuration()). You can also define opCast to do the same thing, but I
> think the ability to avoid typing that dreaded keyword should be available.

I think that it makes good sense to include the opCasts for when they're 
necessary, but I do agree that it would be ideal not to need them. I'd much 
prefer to be using to!() than opCast, but I don't know what the proper way to 
do that is (include overloads for it in core.time and std.datetime?). I didn't 
include functions like toDuration because it seemed silly to create non-
standard, specific functions for that what opCast is intended for. And I don't 
object to opCast casts in the same way that I object to the built in ones, 
since it's really just a function call. But I would prefer that to!() be used, 
since that's appropriately standard and generally safe. I just don't know what 
the proper way to do that is. It seems overkill to add overloads for every 
type in Phobos to std.conv, and that doesn't work for types outside of Phobos 
anyway.

- Jonathan M Davis