How to use a class as key type in AAs?

[JAnderson]

Jarrett Billingsley wrote:
> "Moritz Warning" <moritzwarning at web.de> wrote in message 
> news:g4r043$28f$1 at digitalmars.com...
>> I've read the docs and implemented size_t getHash, int opEquals(Object o)
>> and int opCmp(Object o); but it still doesn't work.
>>
>> The following code prints out: 2 2 1
>>
>> Btw.: I tested (new Foo(1)) == (new Foo(1)) and it gives true,
>> (new Foo(1)) == (new Foo(2)) gives false.
>>
>>
>> void main()
>> {
>> class Foo
>> {
>> uint i;
>> this(uint i ) { this.i = i; }
>>
>> size_t getHash()
>> {
>> return this.i;
>> }
>>
>> int opEquals(Object o)
>> {
>> auto t = cast(Foo) o;
>> if(t is null) return false;
>> return (this.i == t.i);
>> }
>>
>> int opCmp(Object o)
>> {
>> return opEquals(o);
>> }
>> }
> 
> You don't have opCmp implemented correctly.  opEquals returns true if they 
> are equal, while opCmp returns 0.
> 
> It should be
> 
> int opCmp(Object o)
> {
>     auto t = cast(Foo)o;
>     if(t is null)
>         return 1;
> 
>     return i < t.i ? -1 : i > t.i ? 1 : 0;
> } 
> 
> 

Or just

int opCmp(Object o)
{
     auto t = cast(Foo)o;
     if(t is null)
         return 1;

     return i - t.i;
}

-Joel