\( \newcommand{\E}{\mathrm{E}} \) \( \newcommand{\A}{\mathrm{A}} \) \( \newcommand{\R}{\mathrm{R}} \) \( \newcommand{\N}{\mathrm{N}} \) \( \newcommand{\Q}{\mathrm{Q}} \) \( \newcommand{\Z}{\mathrm{Z}} \) \( \def\ccSum #1#2#3{ \sum_{#1}^{#2}{#3} } \def\ccProd #1#2#3{ \sum_{#1}^{#2}{#3} }\)
CGAL 4.12 - STL Extensions for CGAL
STL_Extension/Default.cpp
#include <CGAL/Default.h>
#include <CGAL/use.h>
// A is a concrete type
struct A {};
void use_a(A) {}
// B is the template class which has 2 template parameters
// with default arguments : A and int.
template < typename A1_ = A, typename A2 = int >
struct B
{
B()
: a1()
{}
// Note that it is also possible to use CGAL::Default
// instead of A as the default argument for A1_ above.
// Extract the desired type for A1 :
typedef typename CGAL::Default::Get<A1_, A>::type A1;
A1 a1;
};
int main ()
{
B<CGAL::Default, double> b;
use_a(b.a1); // It is really of type A.
}