Ideas from the Chapel language (swap)

[Robert Fraser]

Gregor Richards Wrote:

> Derek Parnell wrote:
> > On Wed, 03 Oct 2007 14:53:57 -0400, Bruce Adams wrote:
> > 
> >> bearophile Wrote:
> >>
> >>> The Cray Inc is designing the Chapel Language:
> >>> http://chapel.cs.washington.edu/
> >>> The following notes are from the specification V. 0.750:
> >>> http://chapel.cs.washington.edu/spec-0.750.pdf
> >>> I think it's rather cute, it looks like a cross between C++, Fortress and Python. Here are few things I think can be interesting for D designers too:
> >>>
> >>> - Chap. 11.5 page 65, swap operator (useful but probably not enough to justify a new operator)
> >> swap is very useful especially in exception safe programming.
> >> I would like to see swap used as the default implementation of D's transfer constructor (and C++0x's forthcoming move constructor)
> > 
> > Isn't a simple template such this sufficient?
> > 
> > template swap(TYPE)
> > {
> >     void swap(ref TYPE a, ref TYPE b)
> >     {
> >         synchronized
> >         {
> >           TYPE temp = a;
> >           a = b;
> >           b = temp;
> >         }
> >     }
> > 
> > }
> > 
> > 
> 
> For the ridiculously-insane:
> 
> void swap(T)(ref T a, ref T b)
> {
>      synchronized {
>          // this should be some kind of static for ...
>          for (size_t i = 0; i < (a.sizeof/size_t.sizeof); i++) {
>              (cast(size_t*) &a)[i] ^= (cast(size_t*) &b)[i];
>              (cast(size_t*) &b)[i] = (cast(size_t*) &a)[i] ^ 
> (cast(size_t*) &b)[i];
>              (cast(size_t*) &a)[i] ^= (cast(size_t*) &b)[i];
>          }
>      }
> }
> 
> Add some loop unrolling and that's more efficient than memcpy :P
> 
>   - Gregor Richards
> 
> PS: /me <3 XOR swapping

I was just going to mention that; you beat me to it!