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["zengming" <>]

Thank you, I understand. I thought the type of results would only be Point_3.

 

 

2009-03-06

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zengming

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发件人： Pedro_Machado_Manh�es_de_Castro

发送时间： 2009-03-06  16:51:34

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主题： Re: Re: [cgal-discuss] how to output a point's coordinate

Hi!

I think that what you probably want is a Circular_arc_point_3.
Since this line:
assign(pt3, intersecs[0]);
should not work as the type of pt3 is a Point_3 and the type of intersecs[0] is Circular_arc_point_3, your pt3 may keep to be uninitialized.

"Should not work" in this case means "assign(pt3, intersecs[0]);" will return 0, but wont assign anithing to pt3.

As your intersection (considering r = 1) is probably (0, 0, 0), that would "work" (because the value of an uninitialized pt3 would be (0,0,0) ).

The main difference between Point_3 and Circular_arc_point_3 is that Point_3 stores rationals as coordinates while Circular_arc_point_3 stores algebraic numbers of degree 2 (Root_of_2).
This happens because the intersection between 3 rational spheres (or 2 rational circles) may not be representable by rationals, however they are representable by Root_of_2.
By rational spheres (circles) I mean spheres with a rational center (placed on rational coordinates) and with rational squared radius.

So look at what Tom said and prefer using Circular_arc_point_3 instead of Point_3, because only the first one really works.

Pedro

PS: don't overlook the case where the intersection of three spheres can be a Circle_3 or even a Sphere_3.

On Fri, Mar 6, 2009 at 9:22 AM, zengming <> wrote:

 I saw the result by your method, thanks!

 

 

2009-03-06

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zengming

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发件人： Samuel Hornus

发送时间： 2009-03-06  16:13:53

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主题： Re: [cgal-discuss] how to output a point's coordinate

"zengming"  < > wrote:

>  Point_3 pt3;

>  assign(pt3, intersecs[0]); 

> 

> //how can I output the coordinate of point pt3? 

 

The following should work:

 

std::cout  < < pt3;

 

-- 

sam

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