"Overlapping array copy" exception sorting an array of Tuples

[André Stein]

Hi,

Thanks first for your detailed reply!

On 03/07/2011 07:21 PM, Jonathan M Davis wrote:
> Well, Tuple _is_ a struct, so if it's failing with Tuple, it's not going to work
> with just any struct (though apparently it works just fine with the struct that
> you wrote). Regardless, it definitely sounds like a bug in sort (or something
> that sort uses). You should probably open a bug for it:
>
> http://d.puremagic.com/issues/
>
> Though honestly, I don't know why you'd want to use a tuple in this case. I tend
> to think that if you're going to name the fields, you might as well declare a
> struct, but whatever.

I started using Tuples only but I used the naming feature to exchange 
the Tuple and struct implementations easily. Anyway this is no 
production code, just test code to learn D :) Anyway I'll open a bug for 
it. Thanks for the link!


> Oh, on a side note, your opCmp is wrong on two counts. First off, its signature
> should be
>
> int opCmp(ref const TestT rhs) const
>
> I don't think that sort even calls you opCmp, because its signature is wrong
> (arguably, the compiler is currently overly picky about the signature for
> opEquals and opCmp, but they _must_ be exact). So, the default comparison is
> being used, not your opCmp.

I tried both signatures of opCmp but the result seemed the same (both 
sequences of structs sorted correctly). So I wonder what is the default 
comparison of a user defined struct type? Not implementing an opCmp 
function lead to a compiler error..

> The second problem (which you may know about but not have cared) is that using
> subtraction like that in opCmp is going to fail if the numbers are large enough
> that you get overflow. For a completely correct comparison function which uses
> integral types, you need to actually do proper comparisons, not subtract them.
> If you _know_ that your numbers are small enough though, it doesn't actually
> matter, since you'll never get an overflow.

I actually didn't care about that problem but I _will_ do that in future.

Regards,
André