opCmp

[Gor Gyolchanyan]

http://d.puremagic.com/issues/show_bug.cgi?id=7430
Please vote on this, so it would get some attention.

On Fri, Feb 3, 2012 at 8:45 PM, Daniel Murphy <yebblies at nospamgmail.com> wrote:
> Bug!
>
> "Ali Çehreli" <acehreli at yahoo.com> wrote in message
> news:jgh2nb$rtv$1 at digitalmars.com...
>> 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.