From e650e5e1abcb615869bf9cfdb2d277ce70b9ef20 Mon Sep 17 00:00:00 2001
From: Alfredo Correa <alfredo.correa@gmail.com>
Date: Tue, 11 Feb 2025 23:49:22 -0800
Subject: [PATCH] allow use of 1d array iterator as pointer argument

---
 include/boost/multi/array_ref.hpp | 13 ++++++++-----
 test/array_ref.cpp                | 23 ++++++++++++++++++++++-
 2 files changed, 30 insertions(+), 6 deletions(-)

diff --git a/include/boost/multi/array_ref.hpp b/include/boost/multi/array_ref.hpp
index 2101239df..446bf6f05 100644
--- a/include/boost/multi/array_ref.hpp
+++ b/include/boost/multi/array_ref.hpp
@@ -497,6 +497,9 @@ struct array_iterator  // NOLINT(fuchsia-multiple-inheritance) for facades
 	>;
 	using const_reference = const_subarray<element, D - 1, element_ptr>;  // TODO(correaa) should be const_subarray (base of subarray)
 
+	template<class Element2>
+	using rebind = array_iterator<std::decay_t<Element2>, D, typename std::pointer_traits<ElementPtr>::template rebind<Element2>, IsConst, IsMove, Stride>;
+
 	using iterator_category = std::random_access_iterator_tag;
 
 	constexpr static dimensionality_type rank_v = D;
@@ -2376,6 +2379,9 @@ struct array_iterator<Element, 1, Ptr, IsConst, IsMove, Stride>  // NOLINT(fuchs
 	using iterator_concept = typename stride_traits<Stride>::category;
 	using element_type = typename std::pointer_traits<Ptr>::element_type;  // workaround for clang 15 and libc++ in c++20 mode
 
+	template<class Element2>
+	using rebind = array_iterator<std::decay_t<Element2>, 1, typename std::pointer_traits<Ptr>::template rebind<Element2>, IsConst, IsMove, Stride>;
+
 	static constexpr dimensionality_type dimensionality = 1;
 
 	#if __cplusplus >= 202002L
@@ -3625,11 +3631,8 @@ class array_ref : public subarray<T, D, ElementPtr, Layout>
 #pragma clang diagnostic pop
 #endif
 
-template<class T, dimensionality_type D, class Ptr = T*>
-using array_cref = array_ref<
-	std::decay_t<T>, D,
-	typename std::pointer_traits<Ptr>::template rebind<T const>
->;
+template<class T, dimensionality_type D, class Ptr = typename std::pointer_traits<T*>::template rebind<T const> >
+using array_cref = array_ref<std::decay_t<T>, D, Ptr>;
 
 template<class T, dimensionality_type D, class Ptr = T*>
 using array_mref = array_ref<
diff --git a/test/array_ref.cpp b/test/array_ref.cpp
index 0b1de8acb..e9da7d945 100644
--- a/test/array_ref.cpp
+++ b/test/array_ref.cpp
@@ -1,4 +1,4 @@
-// Copyright 2019-2024 Alfredo A. Correa
+// Copyright 2019-2025 Alfredo A. Correa
 // Copyright 2024 Matt Borland
 // Distributed under the Boost Software License, Version 1.0.
 // https://www.boost.org/LICENSE_1_0.txt
@@ -243,6 +243,27 @@ BOOST_AUTO_TEST_CASE(array_ref_test_no_ub) {
 	BOOST_TEST( std::accumulate(diag.begin(), diag.end(), 0) == 0 + 60 + 120 + 180 );
 }
 
+/*use iterator as pointer*/
+{
+	multi::array<int, 1> const arr = {1, 2, 3, 4, 5, 6};
+	multi::array_ref<int, 2, multi::array<int, 1>::const_iterator> const arr2({2, 3}, arr.begin());
+	BOOST_TEST(( arr2 == multi::array{
+		{1, 2, 3},
+		{4, 5, 6}
+	}));
+}
+
+/*use iterator as pointer*/
+{
+	// multi::array<int, 2> const arr = { {1, 2}, {3, 4}, {5, 6}, {7, 8}};
+	// multi::array_ref<int, 2, multi::array<int, 2>::const_iterator> const arr2({2, 2}, arr.begin());
+	// BOOST_TEST(( arr2 == multi::array{
+	// 	{1, 2, 3},
+	// 	{4, 5, 6}
+	// }));
+}
+
+
 BOOST_AUTO_TEST_CASE(array_ref_test_no_ub2) {
 	#if defined(__clang__)
 	#pragma clang diagnostic push