From 2a8a32d6ad485772640de1532c71c451dbb3e3dd Mon Sep 17 00:00:00 2001
From: Laurent Rineau <laurent.rineau@cgal.org>
Date: Fri, 19 Sep 2025 11:53:02 +0200
Subject: [PATCH] fix Prevent_deref<Union_find::iterator>

`std::iterator_traits` requires that the iterator type defines all five nested types.

I have also modified the implementation of

```c++
make_prevent_deref_range(Range)
```
---
 STL_Extension/include/CGAL/iterator.h | 14 ++++++++------
 Union_find/include/CGAL/Union_find.h  |  3 +++
 2 files changed, 11 insertions(+), 6 deletions(-)

diff --git a/STL_Extension/include/CGAL/iterator.h b/STL_Extension/include/CGAL/iterator.h
index b93190ded73..8f8a2228b07 100644
--- a/STL_Extension/include/CGAL/iterator.h
+++ b/STL_Extension/include/CGAL/iterator.h
@@ -69,12 +69,6 @@ private:
   }
 };
 
-template<typename I>
-Iterator_range<Prevent_deref<I> > make_prevent_deref_range(const Iterator_range<I>& range)
-{
-  return Iterator_range<Prevent_deref<I> >(make_prevent_deref(range.first), make_prevent_deref(range.second));
-}
-
 template<typename I>
 Prevent_deref<I> make_prevent_deref(const I& i)
 {
@@ -87,6 +81,14 @@ Iterator_range<Prevent_deref<I> > make_prevent_deref_range(const I& begin, const
   return Iterator_range<Prevent_deref<I> >(make_prevent_deref(begin), make_prevent_deref(end));
 }
 
+template<typename R>
+auto make_prevent_deref_range(const R& range)
+{
+  using std::begin;
+  using std::end;
+  return make_range(make_prevent_deref(begin(range)), make_prevent_deref(end(range)));
+}
+
 namespace cpp98 {
 
 template<typename Category, typename Tp, typename Distance = std::ptrdiff_t,
diff --git a/Union_find/include/CGAL/Union_find.h b/Union_find/include/CGAL/Union_find.h
index 16dc14bdb74..1db665ffa0d 100644
--- a/Union_find/include/CGAL/Union_find.h
+++ b/Union_find/include/CGAL/Union_find.h
@@ -22,6 +22,7 @@
 #include <CGAL/basic.h>
 #include <CGAL/memory.h>
 #include <cstddef>
+#include <iterator>
 
 namespace CGAL {
 
@@ -39,6 +40,7 @@ public:
     typedef R_                                    reference;
     typedef P_                                    pointer;
     typedef std::forward_iterator_tag             iterator_category;
+    typedef std::ptrdiff_t                        difference_type;
 
     UF_forward_iterator() : m_p(0) {}
     UF_forward_iterator(PTR_ p) : m_p(p) {}
@@ -104,6 +106,7 @@ public:
     typedef T                                                value_type;
     typedef T&                                               reference;
     typedef const T&                                         const_reference;
+    typedef std::forward_iterator_tag                        iterator_category;
 
     typedef internal::UF_forward_iterator< pointer, T, T&, T*>  iterator;
     typedef iterator                                         handle;