sort error

[snow]

On Saturday, 29 June 2013 at 14:20:05 UTC, Ali Çehreli wrote:
> On 06/29/2013 05:46 AM, snow wrote:
>
> > On Friday, 28 June 2013 at 17:07:22 UTC, Ali Çehreli wrote:
>
> >> Your opCmp does not provide a complete ordering of objects:
> >>
> >>     int opCmp(ref const Vector3D vec) {
> >>         if (this.x > vec.x && this.y > vec.y && this.z >
> vec.z)
> >>             return 1;
> >>
> >>         if (this.x < vec.x && this.y < vec.y && this.z <
> vec.z)
> >>             return -1;
> >>
> >>         return 0;
> >>     }
> >>
> >> According to that function, the following two values are
> neither less
> >> than nor greater than the other:
> >>
> >>     // passes:
> >>     assert(!(Vector3D(1, 2, 3) < Vector3D(2, 1, 3)) &&
> >>            !(Vector3D(1, 2, 3) > Vector3D(2, 1, 3)));
> >>
> >> Ali
> >
> > I tried this now:
> >      int opCmp(ref const Vector3D vec) {
> >          if (this.x > vec.x && this.y > vec.y && this.z >
> vec.z)
> >              return 1;
> >          return -1;
> >      }
> > this should be a total ordering,
>
> Unfortunately, no. opCmp must return 0 when the values are 
> considered equal.
>
> > because a Vector is always greater or smaller, than another,
> > but I still get the same exception.
>
> Not knowing whether it applies to your case, the following is 
> one almost correct way of writing opCmp:
>
>     int opCmp(ref const Vector3D vec) {
>         return cast(int)(x != vec.x
>                          ? x - vec.x
>                          : (y != vec.y
>                             ? y - vec.y
>                             : z - vec.z));
>     }
>
> The reason I said "almost" is due to the usual floating point 
> equality comparison warnings. Values that are supposed to be 
> equal may not compare equal due to accumulated earlier floating 
> point calculation errors.
>
> Ali

Thats a cool way, thanks. But the exception is still coming. Both 
solutions  throw -1,0 or 1. So my first solution should work, 
too. Sure that the exception is coming, because of the compare 
function?