On Mon, 26 Dec 2011 00:37:22 +1100, Chris Angelico wrote:
> On Mon, Dec 26, 2011 at 12:27 AM, Steven D'Aprano
> <steve+comp.lang.pyt...@pearwood.info> wrote:
>> There's nothing in the above that assumes that other has the same type
>> as self. It's just that the type of other is ignored, and the type of
>> self always wins. I find that a nice, clear rule: x.intersection(y)
>> always returns a point with the same type as x.
>
> The intersection of DrawableLine and DrawableLine is DrawablePoint.
> That's not the same type as either of the inputs. Same if you seek the
> intersection of two planes, which is a line - or two spheres, which is a
> circle (with possible failure if they don't intersect).
class Line:
intersection_kind = Point
def intersection(self, other):
blah()
return self.intersection_kind(a, b)
class DrawableLine(Line):
intersection_kind = DrawablePoint
--
Steven
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