Re: opEquals optimized away?

[Manfred Nowak via Digitalmars-d-learn]

On Tuesday, 5 May 2015 at 05:26:17 UTC, anonymous wrote:


because `c is c`


Thanks. One can see this documented in
  http://dlang.org/operatoroverloading.html#equals

But
1: how can one override this behavior
2: what is the design reason for this

Especially: how can one implement side effects on invoking `==' 
or `!='?


-manfred

Re: opEquals optimized away?

[Ali Çehreli via Digitalmars-d-learn]

On 05/05/2015 04:30 PM, Manfred Nowak wrote:
 On Tuesday, 5 May 2015 at 05:26:17 UTC, anonymous wrote:

 because `c is c`

 Thanks. One can see this documented in
http://dlang.org/operatoroverloading.html#equals

 But
 1: how can one override this behavior

There is now way in D other than changing the implementation:


https://github.com/D-Programming-Language/druntime/blob/master/src/object_.d#L141

(There is also object.di there but I think changing the function above 
should be sufficient.)


 2: what is the design reason for this

I am guessing:

- For correctness, an object should be equal to itself

- Preventing memory errors when the left-hand side object is null.

- Reducing boilerplate

 Especially: how can one implement side effects on invoking `==' or `!='?

 -manfred

Can you use a member function instead as in c.eq(c)?

Ali

opEquals optimized away?

[Manfred Nowak via Digitalmars-d-learn]

class C{
  override bool opEquals( Object o){
return true;
  }
}
unittest{
  auto c= new C;
  assert( c == c);
}

`rdmd --main -unittest -cov' shows, that opEquals is not 
executed. Why?


-manfred

Re: opEquals optimized away?

[anonymous via Digitalmars-d-learn]

On Tuesday, 5 May 2015 at 04:09:03 UTC, Manfred Nowak wrote:

class C{
  override bool opEquals( Object o){
return true;
  }
}
unittest{
  auto c= new C;
  assert( c == c);
}

`rdmd --main -unittest -cov' shows, that opEquals is not 
executed. Why?


-manfred


because `c is c`

https://github.com/D-Programming-Language/druntime/blob/0ac255d7276b9b825eb6f1e677e9ee4f5ad49ca2/src/object.di#L61