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["Pedro Machado Manhães de Castro" <>]

On Sun, Oct 19, 2008 at 2:44 PM, <> wrote:

I have computed two points from circle intersect,  it's type is
Circular_arc_point_2 , How to construct a Line_arc_2?

You can't create a line_arc_2 only from 2 circular_arc_point_2 because there is no guarantee the underlying line_2 is rational (has its coefficients rational).
However, when known that you had them by an intersection of 2 circles, you know that the underlying line_2 is rational.
So there is a constructor:

Line_arc_2<CircularKernel> la (

CircularKernel::Line_2 l, CircularKernel::Circular_arc_point_2 p1, CircularKernel::Circular_arc_point_2 p2);

That you should use instead.
The line_2 in question is the radical line from the two circles.
You can have it doing, for example, that:
Circle_2 c1, c2; // your circles
FT a = 2*(c2.center().x() - c1.center().x());
FT b = 2*(c2.center().y() - c1.center().y());
FT c = (c1.center().x()) * (c1.center().x()) +
           (c1.center().y()) * (c1.center().y()) - c1.squared_radius() -
           (c2.center().x()) * (c2.center().x()) -
           (c2.center().y()) * (c2.center().y()) + c2.squared_radius();
Line_2 l = Line_2(a, b, c);
Line_arc_2 la = Line_arc_2(l, p1, p2);

Cheers,
Pedro
 

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