CGAL users discussion list

[Martin Seemann <>]

Dear CGAL folks,

I recently came across a regression, which is demonstrated by the 
example below:

#include <CGAL/Simple_cartesian.h>
int main() {    
        typedef CGAL::Simple_cartesian<double> K;
	CGAL::Line_3<K> line(CGAL::Point_3<K>(0, 0, 0), CGAL::Point_3<K>(1, 
1, 1));	
        std::cout << line.point(0) << std::endl;
        return 0;       
}

Using GCC 5.2.0 (Archlinux), the above example compiles fine with 
-std=c++11 but when switching to -std=c++14, the compiler starts 
complaining about ambiguous 'get(...)' overloads in 
CGAL/Cartesian/Line_3.h:78.
I figured that it was caused by some c++14 additions to the standard 
library (http://en.cppreference.com/w/cpp/utility/pair/get, overloads 4-7).
A quick fix is to make the desired namespace explicit in 
CGAL/Cartesian/Line_3.h, i. e. to replace lines 78 and 83 by
    return CGAL::get(base).first;
and
    return CGAL::get(base).second;
respectively.
After these modifications, the above example (and also my real project) 
compiles fine.

However, prefixing with CGAL:: in this place seems strange to me, since 
we are already in namespace CGAL. Furthermore, I do not understand why 
the std::get variants even participate in overload resolution, given 
that they are defined in std (I couldn't find any dangerous
'using namespace std' anywhere in the CGAL code base either).

Maybe someone with a deeper understanding of the language can give his 
opinion if this situation should be corrected in CGAL or in the standard 
library.
BTW: The error also happens with clang (v3.6.2)
(My CGAL version is 4.6.2)

Greets,
Martin