array cast should be supported corrected

[Bill Baxter]

On Thu, Aug 7, 2008 at 6:06 AM, BCS <ao at pathlink.com> wrote:
> Reply to Frank,
>
>> However. What is better in a template arraycast with o(n) or a cast?
>> The programmer always needs to know what the concequences are. With
>> this argumentation the string concatenation ~ should also be banned from
>> the language, because hidden heap allocation has always unbound execution
>> time.
>
> Array cat's /always/ do a O(?) allocation and a O(n+m) copy.

Not true for ~=.  Sometimes allocates sometimes doesn't.  You'll have
to come up with a better argument than that. :-)

That said, I don't see why writing arraycast!(T)(x) is so much worse
than cast(T)x.  I wish D had more flavors of cast.  The current cast
is a very blunt instrument.  Seems obvious to me that It's a bad idea
to use the same construct to mean "please convert this to a T" and
"please pretend the bits of this are actually bits of a T".  C++ added
all those extra kinds of casts for a reason.

> Cast usually
> does a O(1) transformation. Having the corner case be much worse than the
> normal case is the problem, not the fact it's O(n).

I think casting to an interface is O(n) in the number of interfaces
the object supports, no?

--bb