opEquals footprint

[xs0]

Erik Rasmussen wrote:
> xs0 wrote:
>> int opEquals(Object)
>>
>> so it overrides the default implementation found in, you guessed it, 
>> Object :) Same goes for opCmp, I think..
>>
>>
>> xs0
> 
> So what's the best way to actually check the type in the opEquals/opCmp 
> method?  Something like...
> 
> class A
> {
>   int opEquals(Object o)
>   {
>     // check for null
>     if(o is null)
>       return false;
>     // check type
>     if(typeid(typeof(o)) != typeid(A))
>       return false;
>     // cast
>     A that = cast(A) o;
>     // actually check fields
>     return this.a == that.a && this.b == that.b && ...;
>   }
> }
> 
> Or is there a better way?  asserts?
> 
> How do you hard-core D programmers usually do it?
> 
> Cheers,
> Erik

Something like this should be ok:

// optional
if (this is o)
     return true;

if (A that = cast(A)o) { // checks for null, too
     return this.a==that.a && ...
} else {
     return false;
}

OTOH, if you want to return false for subclasses, your version seems 
fine to me.


xs0