On Sun, 31 Mar 2013 06:00:53 -0400, Lars T. Kyllingstad
<pub...@kyllingen.net> wrote:
On Saturday, 30 March 2013 at 02:46:27 UTC, Steven Schveighoffer wrote:
On Fri, 29 Mar 2013 18:08:28 -0400, Jonathan M Davis
<jmdavisp...@gmx.com> wrote:
std.conv.to is the standard way to convert one type to another. I see
no
reason to introduce stuff specific to core.time or std.datetime to do
conversions. It should just hook into the standard stuff for that. If
everything uses std.conv.to for coverting between types, then you
don't have
to worry about figuring out how a particular programmer decided that
their API
should do it - be it with casts or asOtherType toOtherType or whatever.
std.conv.to is specifically designed so that any type can hook their
own
conversions into it, and then you can just always use std.conv.to for
converting types.
But the one doing the work is core.time. In essence, you have locked
away part of the API behind cast, and in order to get it out without
using cast, you have to import another module.
opCast is just a function, it could easily be called opTo, or simply
to(T)().
Now that we have the UFCS, std.conv.to should simply be implemented as:
T to(F, T)(F from)
{
T t;
from.convert(t);
return t;
}
Then, std.conv should provide convert() functions for built-in types,
e.g.
void convert(wstring from, ref string to);
void convert(long from, ref int to);
etc.
User-defined types could define their own convert method:
struct MyType
{
void convert(ref MyOtherType tgt);
}
This is both safer and more flexible than using opCast(), since
1. you avoid the unfortunate association with the cast operator,
2. convert() can be virtual if desired,
3. convert() can be called directly to modify the target variable
in-place.
I don't think this is flexible enough. It may not be enough to be able to
fill in another type.
But we don't need to go through ANY of this, just change T opCast(T)() to
T to(T)().
This way, with UFCS, a.to!B() will either call the method if available, or
std.conv.to (assuming it's imported).
-Steve
