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Template Dispatcher question

chameleon (57)
FIXED!! Now It's not unsafe (see 1st comment).

The code below completely avoid rtti but it is a little bit difficult to maintain.
Is there a template way to eliminate group of virtual functions in GeometryPlace?
Thanks!

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struct GeometryPlace
{
   virtual const GeometryPlace *intersect(const GeometryPlace *gp) const = 0;
   .........
   virtual const GeometryPlace *intersect(const class CircleArc2 *gp) const {}
   virtual const GeometryPlace *intersect(const class LineSegment2 *gp) const {}
   virtual const GeometryPlace *intersect(const class SemiPlan2 *gp) const {}
   virtual const GeometryPlace *intersect(const class Point3 *gp) const {}
   virtual const GeometryPlace *intersect(const class PlaceUnion *gp) const {}
   .........
   static const class GeometryPlace *intersect(const class CircleArc2 *c1, const class CircleArc2 *c2);
   .........
   .........
};

template <typename T>
struct IntersectDispatch : public GeometryPlace
{
   virtual const GeometryPlace *intersect(const GeometryPlace *gp) const
      { return gp->intersect(static_cast<const T*>(this)); }

   virtual const GeometryPlace *intersect(const class CircleArc2 *gp) const
      { return GeometryPlace::intersect(static_cast<const T*>(this), gp); }
   .........
   virtual const GeometryPlace *intersect(const class PlaceUnion *gp) const
      { return GeometryPlace::intersect(static_cast<const T*>(this), gp); }
};

struct CircleArc2 : public IntersectDispatch<CircleArc2> {}
.........
Last edited on
helios (17574)
static_cast<const T*>(this)
I'm fairly sure this is unsafe.

What prevents someone from doing this?
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//class A:GeometryPlace{...};

A foo;
CircleArc2 ca;
ca.intersect(&foo);


Why do you want to avoid RTTI?
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