From 993b36515c767476a96ec7bbdbfc9d2178f28888 Mon Sep 17 00:00:00 2001
From: Barend Gehrels <barend@xs4all.nl>
Date: Sat, 23 Mar 2024 11:16:54 +0100
Subject: [PATCH] [fix] replace decltype by typename for some compilers

---
 .../detail/sections/sectionalize.hpp          | 29 ++++++++++++-------
 1 file changed, 18 insertions(+), 11 deletions(-)

diff --git a/include/boost/geometry/algorithms/detail/sections/sectionalize.hpp b/include/boost/geometry/algorithms/detail/sections/sectionalize.hpp
index 3317ff70a..d9cd95885 100644
--- a/include/boost/geometry/algorithms/detail/sections/sectionalize.hpp
+++ b/include/boost/geometry/algorithms/detail/sections/sectionalize.hpp
@@ -721,24 +721,31 @@ struct sectionalize_multi
 template <typename Sections, typename Strategy>
 inline void enlarge_sections(Sections& sections, Strategy const&)
 {
-    // Expand the box to avoid missing any intersection. The amount is
-    // should be larger than epsilon. About the value itself: the smaller
-    // it is, the higher the risk to miss intersections. The larger it is,
-    // the more comparisons are made, which is not harmful for the result
-    // (but it might be for the performance).
-    // So it should be on the high side.
-
-    // Use a compilable and workable epsilon for all types, for example:
+    // Expand the box to avoid missing any intersection.
+    // About the value itself: the smaller it is,
+    // the higher the risk to miss intersections.
+    // The larger it is, the more comparisons are made,
+    // which is not harmful for the result,
+    // but it might be for the performance.
+    // So it should be on the higher side.
+    //
+    // The current value:
     // - for double :~ 2.22e-13
     // - for float  :~ 1e-4
     // - for Boost.Multiprecision (50) :~ 5.35e-48
     // - for Boost.Rational : 0/1
 
+    // WARNING: don't use decltype here.
+    // Earlier code used decltype(section.bonding_box) below,
+    // but that somehow is not accepted by the NVCC (CUDA 12.4) compiler.
+    using section_t = typename boost::range_value<Sections>::type;
+    using box_t = typename section_t::box_type;
+    using coor_t = typename geometry::coordinate_type<box_t>::type;
+
+    static auto const eps = math::scaled_epsilon<coor_t>(1000);
+
     for (auto& section : sections)
     {
-        using gt = decltype(section.bounding_box);
-        using ct = typename geometry::coordinate_type<gt>::type;
-        static ct const eps = math::scaled_epsilon<ct>(1000);
         expand_by_epsilon(section.bounding_box, eps);
     }
 }