CGAL users discussion list

[John Carter <>]

Menelaos, 

Ah, that makes sense.  I was writing the graph segments out to a text file 
and the Stream overload seemed to do the job well enough.  I noticed the 
other overload(Qt) was clearly related to graphically plotting the points, so 
I should've taken a hint.  I'm just abusing the Stream functions as a quick 
and dirty way to dump data into a text file, I suppose.  The behavior just 
seemed inconsistent for text-based streams which is fine since that was never 
their intended use. Writing an ostream& overload would definitely make sense 
in this case and I have since modified the code to do so.  Thanks for the 
fast reply!

Regards,
JC


-----Original Message-----
From: Menelaos Karavelas 
[mailto:]
 
Sent: Monday, August 08, 2011 10:38 PM
To: 

Subject: Re: [cgal-discuss] BUG: CGAL 3.8 Parabola_segment_2.h

This draw method is not intended to write segments on the screen (or in more 
general in ascii mode), but rather to a graphical stream, in which case 
sending spaces does not make any sense (and in that sense it is not a bug).

If you really need to get a polyline approximation to the parabolic arc, then 
I would propose to write another method that sends the polyline to an 
std::ostream. Do you really need the polyline approximation in your 
application? I could add this functionality to the Parabola_2 class.

- m.


On 9 Aug 2011, at 08:25, John Carter wrote:

> Greetings,
> 
> As a first time CGAL user, I'd like to greet the users and thank the 
> community for this great piece of software.
> 
> While sifting through the code to build a polygonal medial axis transform 
> using a Segment_delaunay_graph,  I noticed what appears to be a bug in one 
> of the draw functions.
> 
> I am using CGAL 3.8, Visual Studio 10.0 Premium, and Windows 7 with the 
> Filtered_kernel, and Simple_cartesian<double> coordinates.
> 
> The function for drawing a parabolic edge segment to a stream does not 
> properly output a space, causing adjacent line segments to be merged into 
> the stream incorrectly.  An example of the buggy output for an edge:
> 
> 79.4211 133.286 79.4211 133.28679.4211 133.286 63.5996 134.11363.5996 
> 134.113 58
> 
> As can be seen, "133.28679.4211" should read "133.286 79.4211".
> 
> Although there might be a better way to do it, I implemented a simple fix 
> which seems to work:
> 
> In Parabola_segment_2.h line 155 in the draw(Stream& W) function:
> 
> The line was changed from:
> 
> W << Segment_2(p[i], p[i+1]);
> 
> To :
> 
> W << Segment_2(p[i], p[i+1]) << " ";
> 
> I'm not entirely sure why a space is output between some of the coordinates 
> and not others, but this fixed the problem for me.  I thought it would be 
> worth pointing out if other people have had problems with this in the past.
> 
> Regards,
> John Carter
> GeoDigital International Corp.
> 
> 
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