From 37289c5d92aa4ef9b4203e49746ddd733e984ab1 Mon Sep 17 00:00:00 2001
From: Peter Dimov <pdimov@gmail.com>
Date: Sun, 23 Feb 2025 20:45:50 +0200
Subject: [PATCH] Add to_array

---
 include/boost/array.hpp |  65 ++++++++++++++++++++----
 test/Jamfile.v2         |   1 +
 test/to_array_test.cpp  | 107 ++++++++++++++++++++++++++++++++++++++++
 3 files changed, 163 insertions(+), 10 deletions(-)
 create mode 100644 test/to_array_test.cpp

diff --git a/include/boost/array.hpp b/include/boost/array.hpp
index 601fee8..bea6f98 100644
--- a/include/boost/array.hpp
+++ b/include/boost/array.hpp
@@ -430,17 +430,62 @@ namespace boost {
         return arg.elems;
     }
 
-   template <size_t Idx, typename T, size_t N>
-   BOOST_CXX14_CONSTEXPR T &get(boost::array<T,N> &arr) BOOST_NOEXCEPT {
-       BOOST_STATIC_ASSERT_MSG ( Idx < N, "boost::get<>(boost::array &) index out of range" );
-       return arr[Idx];
-       }
+    template <size_t Idx, typename T, size_t N>
+    BOOST_CXX14_CONSTEXPR T &get(boost::array<T,N> &arr) BOOST_NOEXCEPT
+    {
+        BOOST_STATIC_ASSERT_MSG ( Idx < N, "boost::get<>(boost::array &) index out of range" );
+        return arr[Idx];
+    }
 
-   template <size_t Idx, typename T, size_t N>
-   BOOST_CONSTEXPR const T &get(const boost::array<T,N> &arr) BOOST_NOEXCEPT {
-       BOOST_STATIC_ASSERT_MSG ( Idx < N, "boost::get<>(const boost::array &) index out of range" );
-       return arr[Idx];
-       }
+    template <size_t Idx, typename T, size_t N>
+    BOOST_CONSTEXPR const T &get(const boost::array<T,N> &arr) BOOST_NOEXCEPT
+    {
+        BOOST_STATIC_ASSERT_MSG ( Idx < N, "boost::get<>(const boost::array &) index out of range" );
+        return arr[Idx];
+    }
+
+    template<class T, std::size_t N>
+    BOOST_CXX14_CONSTEXPR array<T, N> to_array( T const (&a)[ N ] )
+    {
+        array<T, N> r = {};
+
+        for( std::size_t i = 0; i < N; ++i )
+        {
+            r[ i ] = a[ i ];
+        }
+
+        return r;
+    }
+
+#if !defined(BOOST_NO_CXX11_RVALUE_REFERENCES)
+
+    template<class T, std::size_t N>
+    BOOST_CXX14_CONSTEXPR array<T, N> to_array( T (&&a)[ N ] )
+    {
+        array<T, N> r = {};
+
+        for( std::size_t i = 0; i < N; ++i )
+        {
+            r[ i ] = std::move( a[ i ] );
+        }
+
+        return r;
+    }
+
+    template<class T, std::size_t N>
+    BOOST_CXX14_CONSTEXPR array<T, N> to_array( T const (&&a)[ N ] )
+    {
+        array<T, N> r = {};
+
+        for( std::size_t i = 0; i < N; ++i )
+        {
+            r[ i ] = a[ i ];
+        }
+
+        return r;
+    }
+
+#endif
 
 } /* namespace boost */
 
diff --git a/test/Jamfile.v2 b/test/Jamfile.v2
index 7243765..02c6464 100644
--- a/test/Jamfile.v2
+++ b/test/Jamfile.v2
@@ -84,6 +84,7 @@ run array_eq_test.cpp ;
 run array_lt_test.cpp ;
 run array_thw_test.cpp ;
 run array_get_test.cpp ;
+run to_array_test.cpp ;
 
 # C++11 constexpr
 
diff --git a/test/to_array_test.cpp b/test/to_array_test.cpp
new file mode 100644
index 0000000..6d4cd83
--- /dev/null
+++ b/test/to_array_test.cpp
@@ -0,0 +1,107 @@
+// Copyright 2025 Peter Dimov
+// Distributed under the Boost Software License, Version 1.0.
+// https://www.boost.org/LICENSE_1_0.txt)
+
+#include <boost/array.hpp>
+#include <boost/core/lightweight_test.hpp>
+#include <boost/config.hpp>
+#include <boost/config/workaround.hpp>
+#include <memory>
+#include <utility>
+
+boost::array<int, 3> f1()
+{
+    boost::array<int, 3> r = {{ 1, 2, 3 }};
+    return r;
+}
+
+boost::array<int, 3> const f2()
+{
+    boost::array<int, 3> r = {{ 1, 2, 3 }};
+    return r;
+}
+
+int main()
+{
+    {
+        int a[] = { 1, 2, 3 };
+
+        boost::array<int, 3> b = boost::to_array( a );
+
+        BOOST_TEST_EQ( b[0], 1 );
+        BOOST_TEST_EQ( b[1], 2 );
+        BOOST_TEST_EQ( b[2], 3 );
+    }
+
+    {
+        int const a[] = { 1, 2, 3 };
+
+        boost::array<int, 3> b = boost::to_array( a );
+
+        BOOST_TEST_EQ( b[0], 1 );
+        BOOST_TEST_EQ( b[1], 2 );
+        BOOST_TEST_EQ( b[2], 3 );
+    }
+
+    {
+        boost::array<int, 3> b = boost::to_array( f1().elems );
+
+        BOOST_TEST_EQ( b[0], 1 );
+        BOOST_TEST_EQ( b[1], 2 );
+        BOOST_TEST_EQ( b[2], 3 );
+    }
+
+    {
+        boost::array<int, 3> b = boost::to_array( f2().elems );
+
+        BOOST_TEST_EQ( b[0], 1 );
+        BOOST_TEST_EQ( b[1], 2 );
+        BOOST_TEST_EQ( b[2], 3 );
+    }
+
+#if BOOST_CXX_VERSION >= 201103L
+
+#if !BOOST_WORKAROUND(BOOST_MSVC, < 1910)
+    {
+        int a[] = { 1, 2, 3 };
+
+        boost::array<int, 3> b = boost::to_array( std::move( a ) );
+
+        BOOST_TEST_EQ( b[0], 1 );
+        BOOST_TEST_EQ( b[1], 2 );
+        BOOST_TEST_EQ( b[2], 3 );
+    }
+
+    {
+        int const a[] = { 1, 2, 3 };
+
+        boost::array<int, 3> b = boost::to_array( std::move( a ) );
+
+        BOOST_TEST_EQ( b[0], 1 );
+        BOOST_TEST_EQ( b[1], 2 );
+        BOOST_TEST_EQ( b[2], 3 );
+    }
+#endif
+
+    {
+        boost::array<int, 3> b = boost::to_array({ 1, 2, 3 });
+
+        BOOST_TEST_EQ( b[0], 1 );
+        BOOST_TEST_EQ( b[1], 2 );
+        BOOST_TEST_EQ( b[2], 3 );
+    }
+
+#if !BOOST_WORKAROUND(BOOST_MSVC, < 1920)
+    {
+        std::unique_ptr<int> a[] = { {}, {}, {} };
+
+        boost::array<std::unique_ptr<int>, 3> b = boost::to_array( std::move( a ) );
+
+        (void)b;
+    }
+#endif
+
+#endif
+
+    return boost::report_errors();
+}