opCmp

[Gor Gyolchanyan]

How do I overload the unordered comparison operators? do I overload
them one by one? If I do what happens if I also define the opCmp?

On Fri, Feb 3, 2012 at 8:41 PM, Ali Çehreli <acehreli at yahoo.com> wrote:
> On 02/03/2012 06:44 AM, Gor Gyolchanyan wrote:
>> Good day.
>>
>> There's a problem in how opCmp works.
>>
>> I have a structure, that represents an element of a range. Let's say a
>> character. That character can be invalid.
>> I need all comparison operators to return false of at least one of the
>> operands is invalid.
>
> As an observation, you want to implement the concept of "unordered" for
> types, similar to floating point types:
>
>  http://dlang.org/expression.html#floating_point_comparisons
>
> I am very surprised that the following operator works with
> non-floating-point types:
>
> class C
> {
>    override int opCmp(Object o)
>    {
>        return 0;
>    }
> }
>
> void main()
> {
>    auto c = new C;
>    auto b = (c !<>= c);      // <-- compiles!
>
>    int i, j;
>    auto b2 = (i !<>= j);     // <-- compiles!
> }
>
> Is that supported? Is it a bug? Would using those /unordered/ operator help
> in your case?
>
>
>> with opCmp, the expression a @ b is rewritten as a.opCmp(B) @ 0, which
>> doesn't allow me to define such a logic.
>> wouldn't it be better to change the rewrite of opCmp to test for exact
>> values -1, 0 and 1? In that case I could return 2 and have all
>> comparisons fail.
>>
>
> Ali
>



-- 
Bye,
Gor Gyolchanyan.