Operator overloading -- lets collect some use cases

[Andrei Alexandrescu]

Frits van Bommel wrote:
> Don wrote:
>> Andrei Alexandrescu wrote:
>>> Well I forgot whether BigInt is a class, is it? Anyhow, suppose it 
>>> *is* a class and as such has reference semantics. Then a += b 
>>> modifies an object in-situ, whereas a = a + b creates a whole new 
>>> object and happens to bind a to that new object.
>>
>> You're right, though BigInt is not a class. I have, though, seen a 
>> BigIntRef class (in Diemos, I think) which behaved in that way. AFAIK, 
>> the reason it existed was that the only way you can enforce value 
>> semantics in D1 is via copy-on-write, which results in many 
>> unnecessary heap allocations and copies.
>> So Fritz is correct, it could not be enforced for reference types.
> 
> First of all, please note that I'm not German so my name ends with an 
> 's', not a 'z'.
> 
>> The question then is, when are reference semantics desired for an 
>> object with arithmetical operator overloading?
>>
>> For matrix slices, maybe? But even then I'm not certain you'd want to 
>> allow X=X+Y; you'd probably want to use X[]=X[]+Y[].
> 
> I never said it'd be useful to use arithmetic ops with classes. In fact, 
> my suggestion was to just only apply these transformations to structs 
> since they probably wouldn't be very useful for classes anyway.

The problem is that even structs may have reference semantics.

Andrei