From fb3d75763ac3527fe6bdc33384321b4a164cd039 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Loriot?= <sebastien.loriot@cgal.org>
Date: Tue, 5 Nov 2024 10:17:44 +0100
Subject: [PATCH] using functor to iterator over coordinates

---
 .../CGAL/Frechet_distance/internal/curve.h    | 18 ++++++++++----
 .../internal/high_level_predicates.h          | 18 ++++++++------
 .../Frechet_distance_minimal_traits_2.cpp     | 24 +++++++++++++++----
 3 files changed, 43 insertions(+), 17 deletions(-)

diff --git a/Frechet_distance/include/CGAL/Frechet_distance/internal/curve.h b/Frechet_distance/include/CGAL/Frechet_distance/internal/curve.h
index 88b89435ae9..1e1fa8a99f1 100644
--- a/Frechet_distance/include/CGAL/Frechet_distance/internal/curve.h
+++ b/Frechet_distance/include/CGAL/Frechet_distance/internal/curve.h
@@ -163,6 +163,7 @@ class Curve<T, false>
 
     using Squared_distance = typename Traits::Compute_squared_distance_d;
     using Construct_bbox = typename Traits::Construct_bbox_d;
+    using Construct_cartesian_const_iterator_d = typename Traits::Construct_cartesian_const_iterator_d;
 
     using PointID = ID<Point>;
     using Points = std::vector<Point>;
@@ -230,11 +231,16 @@ class Curve<T, false>
     static IFT distance(Point const& p, Point const& q)
     {
       IFT res(0);
+      Construct_cartesian_const_iterator_d ccci;
+
+      auto itp = ccci(p), itq = ccci(q);
+
       for (int d=0;d<Traits::Dimension::value; ++d)
       {
-        std::pair<double,double> ip = to_interval(p[d]);
-        std::pair<double,double> iq = to_interval(q[d]);
+        std::pair<double,double> ip = to_interval(*itp);
+        std::pair<double,double> iq = to_interval(*itq);
         res+=square(IFT(ip)-IFT(iq));
+        ++itp; ++itq;
       }
       return sqrt(res);
     }
@@ -258,10 +264,12 @@ class Curve<T, false>
         std::array<distance_t, dimension> b_coords;
         auto fraction = pt.getFraction().approx;
         distance_t one_m_f = distance_t(1) - fraction;
+        Construct_cartesian_const_iterator_d ccci;
+        auto itp = ccci(point(pt.getPoint()));
+        auto itq = ccci(point(pt.getPoint()+1));
+
         for (int d=0; d<dimension; ++d)
-          //TODO: use Construct_cartesian_const_iterator_d
-          //TODO: use contruct point and add it in the traits concept
-          b_coords[d] = one_m_f * point(pt.getPoint())[d] +  point(pt.getPoint() + 1)[d] * fraction;
+          b_coords[d] = one_m_f * (*itp++) +  (*itq++) * fraction;
 
         if constexpr (dimension==2)
           return Point(b_coords[0], b_coords[1]);
diff --git a/Frechet_distance/include/CGAL/Frechet_distance/internal/high_level_predicates.h b/Frechet_distance/include/CGAL/Frechet_distance/internal/high_level_predicates.h
index 8bbc96ba73e..22189b23b64 100644
--- a/Frechet_distance/include/CGAL/Frechet_distance/internal/high_level_predicates.h
+++ b/Frechet_distance/include/CGAL/Frechet_distance/internal/high_level_predicates.h
@@ -30,7 +30,7 @@ namespace internal {
 // <=> lambda^2 + (2 b / a) * lambda + (c / a) = 0
 // <=> lambda1/2 = - (b / a) +/- sqrt((b / a)^2 - c / a)
 //TODO: use optional!
-template <class FT, class C, class Point, class AFT>
+template <class Traits, class C, class Point, class AFT>
 bool
 fill_lambda(const Point& circle_center,
             const Point& line_start,
@@ -42,12 +42,16 @@ fill_lambda(const Point& circle_center,
             C const& curve2,
             typename C::PointID const& seg_start_id)
 {
+  using FT = typename Traits::FT;
   FT a(0), b(0), c(0);
-  for (auto i = 0; i < C::dimension; ++i)
+  auto ccci = typename Traits::Construct_cartesian_const_iterator_d();
+  auto it_cc = ccci(circle_center), it_s = ccci(line_start), it_e = ccci(line_end);
+
+  for (auto i = 0; i < C::dimension; ++i, ++it_cc, ++it_s, ++it_e)
   {
-    FT start_end_diff = line_end[i] - line_start[i];
+    FT start_end_diff = *it_e - *it_s;
     a += CGAL::square(start_end_diff);
-    FT start_center_diff = line_start[i] - circle_center[i];
+    FT start_center_diff = *it_s - *it_cc;
     b -= start_center_diff * start_end_diff;
     c += square(start_center_diff);
   }
@@ -95,7 +99,7 @@ intersection_interval(Curve<T, true> const& curve1,
   try {
     std::pair<Lambda<C>, Lambda<C>> II;
     // if not empty
-    if (fill_lambda<typename C::distance_t>(
+    if (fill_lambda<typename T::first_type>(
         curve1[center_id], curve2[seg_start_id], curve2[seg_start_id + 1],
         radius.inf(), II, curve1, center_id, curve2,  seg_start_id))
     {
@@ -105,7 +109,7 @@ intersection_interval(Curve<T, true> const& curve1,
     CGAL_assertion(radius.is_point());
     std::pair<Lambda<C>, Lambda<C>> II;
       // if not empty
-    if (fill_lambda<typename Lambda<C>::Rational>(
+    if (fill_lambda<typename T::second_type>(
           curve1.rpoint(center_id), curve2.rpoint(seg_start_id), curve2.rpoint(seg_start_id + 1),
           radius.inf(), II, curve1, center_id, curve2,  seg_start_id))
     {
@@ -131,7 +135,7 @@ intersection_interval(Curve<T, false> const& curve1,
 
     std::pair<Lambda<C>, Lambda<C>> II;
     // if not empty
-    if (fill_lambda<typename C::distance_t>(
+    if (fill_lambda<T>(
         curve1[center_id], curve2[seg_start_id], curve2[seg_start_id + 1],
         radius.inf(), II, curve1, center_id, curve2,  seg_start_id))
     {
diff --git a/Frechet_distance/test/Frechet_distance/Frechet_distance_minimal_traits_2.cpp b/Frechet_distance/test/Frechet_distance/Frechet_distance_minimal_traits_2.cpp
index a9c9d44769c..a170f0252a3 100644
--- a/Frechet_distance/test/Frechet_distance/Frechet_distance_minimal_traits_2.cpp
+++ b/Frechet_distance/test/Frechet_distance/Frechet_distance_minimal_traits_2.cpp
@@ -6,13 +6,14 @@ struct MinimalFrechetTraits {
   using Dimension = CGAL::Dimension_tag<2>;
   using FT = double;
 
-  struct Point_d {
+  struct Point_d
+  {
     Point_d(double, double) {}
 
-    double operator[](int) const
-    {
-        return 0;
-    }
+    //~ double operator[](int) const
+    //~ {
+        //~ return 0;
+    //~ }
   };
 
   struct Compute_squared_distance_d
@@ -31,6 +32,19 @@ struct MinimalFrechetTraits {
     }
   };
 
+  struct Cartesian_const_iterator_d
+  {
+    FT operator*() { return 0; }
+    Cartesian_const_iterator_d& operator++() { return *this;}
+    Cartesian_const_iterator_d operator++(int) { return Cartesian_const_iterator_d(); }
+  };
+
+  struct Construct_cartesian_const_iterator_d
+  {
+    Cartesian_const_iterator_d operator()(Point_d){ return Cartesian_const_iterator_d(); }
+    Cartesian_const_iterator_d operator()(Point_d, int){ return Cartesian_const_iterator_d(); }
+  };
+
 };