Looking at Don Clugston's BigInt code I see usage of "*this":

BigInt opMulAssign(T: BigInt)(T y) {
       *this = mulInternal(*this, y);
         return *this;
     }

I think I know what it does (passes this by reference) but I can't find any documentation that explains the usage. Can anyone point me to a source??

Paul

Paul D. Anderson wrote:
> Looking at Don Clugston's BigInt code I see usage of "*this":
> 
> BigInt opMulAssign(T: BigInt)(T y) {
>        *this = mulInternal(*this, y);
>          return *this;
>      }
> 
> I think I know what it does (passes this by reference) but I can't find any documentation that explains the usage. Can anyone point me to a source??
> 
> Paul
> 
> 
It's passing by value, since BigInt is a struct, not a class. 'this' is a pointer to the struct, so *this is the struct itself. In the case of BigInt, the struct only contains an bool and a dynamic array, for a total of 10 bytes or so, so it's not much bigger than a pointer.

I believe the behaviour of 'this' in structs changed recently (but probably only in D2?) The BigInt wrapper class would be a bit different in D2.

BTW BigInt uses structs, not classes, and part of the reason for this is that you _cannot_ have value semantics with a class.

Don Wrote:

> Paul D. Anderson wrote:
> > Looking at Don Clugston's BigInt code I see usage of "*this":
> > 
> > BigInt opMulAssign(T: BigInt)(T y) {
> >        *this = mulInternal(*this, y);
> >          return *this;
> >      }
> > 
> > I think I know what it does (passes this by reference) but I can't find any documentation that explains the usage. Can anyone point me to a source??
> > 
> > Paul
> > 
> > 
> It's passing by value, since BigInt is a struct, not a class. 'this' is a pointer to the struct, so *this is the struct itself. In the case of BigInt, the struct only contains an bool and a dynamic array, for a total of 10 bytes or so, so it's not much bigger than a pointer.
> 
> I believe the behaviour of 'this' in structs changed recently (but probably only in D2?) The BigInt wrapper class would be a bit different in D2.
> 
> BTW BigInt uses structs, not classes, and part of the reason for this is that you _cannot_ have value semantics with a class.
> 

Thanks, Don.

Paul