From cf71b05937f751715aece9048ce5cf245c1f23ba Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Loriot?= <sebastien.loriot@cgal.org>
Date: Thu, 24 Nov 2016 09:41:41 +0100
Subject: [PATCH] add an overload of CGAL::to_double for Lazy_alpha_nt_3

---
 Alpha_shapes_3/doc/Alpha_shapes_3/CGAL/Alpha_shape_3.h      | 3 ++-
 Alpha_shapes_3/include/CGAL/internal/Lazy_alpha_nt_3.h      | 6 ++++++
 .../Alpha_shapes_3/include/CGAL/_test_cls_alpha_shape_3.h   | 1 +
 3 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/Alpha_shapes_3/doc/Alpha_shapes_3/CGAL/Alpha_shape_3.h b/Alpha_shapes_3/doc/Alpha_shapes_3/CGAL/Alpha_shape_3.h
index 304fb11c1f5..ca797d9979f 100644
--- a/Alpha_shapes_3/doc/Alpha_shapes_3/CGAL/Alpha_shape_3.h
+++ b/Alpha_shapes_3/doc/Alpha_shapes_3/CGAL/Alpha_shape_3.h
@@ -72,7 +72,8 @@ resorting to exact arithmetic). Access to the interval containing the exact valu
 `FT::Approximate_nt approx() const` where `FT::Approximate_nt` is `Interval_nt<Protected>` 
 with `Protected=true`. Access to the exact value is provided through the function 
 `FT::Exact_nt exact() const` where `FT::Exact_nt` depends on the configuration of %CGAL 
-(it is `Gmpq` if `gmp` is available and `Quotient<CGAL::MP_Float>` otherwise). 
+(it is `Gmpq` if `gmp` is available and `Quotient<CGAL::MP_Float>` otherwise).
+An overload for the function `double to_double(FT)` is also available.
 It must be noted that an object of type `FT` is valid as long as the alpha shapes class that creates 
 it is valid and has not been modified. 
 For convenience, classical comparison operators are provided for the type `FT`. 
diff --git a/Alpha_shapes_3/include/CGAL/internal/Lazy_alpha_nt_3.h b/Alpha_shapes_3/include/CGAL/internal/Lazy_alpha_nt_3.h
index 6d4c7f20fe3..02ff302c514 100644
--- a/Alpha_shapes_3/include/CGAL/internal/Lazy_alpha_nt_3.h
+++ b/Alpha_shapes_3/include/CGAL/internal/Lazy_alpha_nt_3.h
@@ -337,6 +337,12 @@ struct Alpha_nt_selector_3:
 
 } //namespace internal
 
+template<class Input_traits, class Kernel_input, bool mode, class Weighted_tag>
+double to_double(const internal::Lazy_alpha_nt_3<Input_traits, Kernel_input, mode, Weighted_tag>& a)
+{
+  return to_double(a.approx());
+}
+
 } //namespace CGAL
 
 #endif //CGAL_INTERNAL_LAZY_ALPHA_NT_3_H
diff --git a/Alpha_shapes_3/test/Alpha_shapes_3/include/CGAL/_test_cls_alpha_shape_3.h b/Alpha_shapes_3/test/Alpha_shapes_3/include/CGAL/_test_cls_alpha_shape_3.h
index f79893edad5..0d251acb720 100644
--- a/Alpha_shapes_3/test/Alpha_shapes_3/include/CGAL/_test_cls_alpha_shape_3.h
+++ b/Alpha_shapes_3/test/Alpha_shapes_3/include/CGAL/_test_cls_alpha_shape_3.h
@@ -111,6 +111,7 @@ _test_cls_alpha_shape_3()
     a1.set_alpha(*alpha_it);
     if (verbose) {
       std::cerr << std::endl;
+      CGAL::to_double(* alpha_it);
       std::cerr << "alpha value " << * alpha_it << std::endl;
     }
     count_faces(a1, verbose);