P3168R1: use a non-pointer iterator type

CMakeLists.txt

@@ -1,3 +1,6 @@
+# /CMakeLists.txt -*-makefile-*-
+# SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
 cmake_minimum_required(VERSION 3.10)
 
 project(beman_optional26 VERSION 0.0.0 LANGUAGES CXX)

Makefile

@@ -1,5 +1,6 @@
 #! /usr/bin/make -f
-# -*-makefile-*-
+# /Makefile -*-makefile-*-
+# SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
 INSTALL_PREFIX?=.install/
 PROJECT?=$(shell basename $(CURDIR))

README.md

@@ -1,11 +1,16 @@
 # Beman.Optional26: C++26 Extensions for std::optional
 
+<!--
+SPDX-License-Identifier: 2.0 license with LLVM exceptions
+-->
+
 This implementation incorporates the C++26 extensions added for `std::optional`. The `Beman.Optional26` library aims to evaluate the stability, the usability, and the performance of these proposed changes before they are officially adopted by WG21 into the C++ Working Draft. Additionally, it allows developers to use these new features before they are implemented in major standard library compilers.
 
 **Implements**:
 * [`std::optional<T&>` (P2988R5)](https://wg21.link/P2988R5)
 * [Give *std::optional* Range Support (P3168R1)](https://wg21.link/P3168R1).
 
+## License
 
 Source is licensed with the Apache 2.0 license with LLVM exceptions
 

cmake/Config.cmake.in

@@ -1,3 +1,6 @@
+# cmake/Config.cmake.in -*-makefile-*-
+# SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
 @PACKAGE_INIT@
 
 include("${CMAKE_CURRENT_LIST_DIR}/@[email protected]")

etc/gcc-flags.cmake

@@ -3,7 +3,7 @@ include_guard(GLOBAL)
 set(CMAKE_CXX_STANDARD 23)
 
 set(CMAKE_CXX_FLAGS
-   "-Wall -Wextra "
+   "-std=c++23 -Wall -Wextra "
 CACHE STRING "CXX_FLAGS" FORCE)
 
 set(CMAKE_CXX_FLAGS_DEBUG "-O0 -fno-inline -g3" CACHE STRING "C++ DEBUG Flags" FORCE)

examples/CMakeLists.txt

@@ -1,3 +1,6 @@
+# examples/CMakeLists.txt -*-makefile-*-
+# SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
 set(BEMAN_OPTIONAL26_LIBRARY "beman_optional26")
 
 include(GNUInstallDirs)

examples/README.md

@@ -1,7 +1,26 @@
 # Beman.Optional26 Examples
 
+<!--
+SPDX-License-Identifier: 2.0 license with LLVM exceptions
+-->
+
 List of usage examples for `Beman.Optional26`.
 
+## License
+Source is licensed with the Apache 2.0 license with LLVM exceptions
+
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+Documentation and associated papers are licensed with the Creative Commons Attribution 4.0 International license.
+
+// SPDX-License-Identifier: CC-BY-4.0
+
+The intent is that the source and documentation are available for use by people implementing their own optional types as well as people using the optional presented here as-is.
+
+The README itself is licesed with CC0 1.0 Universal. Copy the contents and incorporate in your own work as you see fit.
+
+// SPDX-License-Identifier: CC0-1.0
+
 ## Sample
 
 Check [sample](sample.cpp) for basic `Beman.Optional26` library usage.

examples/optional_ref.cpp

@@ -1,3 +1,6 @@
+// examples/optional_ref.cpp -*-C++-*-
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
 #include <Beman/Optional26/optional.hpp>
 
 #include <string>

examples/range_loop.cpp

@@ -1,3 +1,6 @@
+// examples/range_loop.cpp -*-C++-*-
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
 #include <Beman/Optional26/optional.hpp>
 #include <iostream>
 

examples/sample.cpp

@@ -1,3 +1,6 @@
+// examples/sample.cpp -*-C++-*-
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
 #include <Beman/Optional26/optional.hpp>
 #include <iostream>
 

extern/CMakeLists.txt

@@ -1 +1,4 @@
+# extern/CMakeLists.txt -*-makefile-*-
+# SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
 add_subdirectory(googletest EXCLUDE_FROM_ALL)

include/Beman/Optional26/detail/iterator.hpp

@@ -0,0 +1,73 @@
+// include/Beman/Optional26/detail/iterator.hpp -*-C++-*-
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+#ifndef BEMAN_OPTIONAL26_DETAIL_ITERATOR_HPP
+#define BEMAN_OPTIONAL26_DETAIL_ITERATOR_HPP
+
+#include <Beman/Optional26/detail/stl_interfaces/iterator_interface.hpp>
+
+#include <concepts>
+#include <iterator>
+
+namespace beman::optional::detail {
+
+// Forward declaration.
+template <class T, class Container>
+struct contiguous_iterator;
+
+// Base class for contiguous iterator types with Boost stl_interfaces library.
+// Current implementation based on P2727R4: std::iterator_interface.
+template <class T, class Container>
+using base_contiguous_iterator = stl_interfaces::iterator_interface<
+#if !BEMAN_OPTIONAL26_DETAIL_STL_INTERFACES_USE_DEDUCED_THIS
+    contiguous_iterator<T, Container>, // Required for P2727R4 to work with C++20/C++23. TODO: Do more experiments.
+#endif
+    std::contiguous_iterator_tag,
+    T>;
+
+// This is a minimal contiguous iterator.  It uses stl_interfaces library from Boost
+// (current implementation based on https://wg21.link/P2727R4).
+//
+// TODO: Change this to use the stl_interfaces library from Beman if/when available.
+//
+// @tparam T - The type of the elements the iterator points to.
+// @tparam Container - The type of the container the iterator points to. This parameter exists solely so that different
+// containers using this template can instantiate different types, even if the T parameter is the same.
+template <class T, class Container>
+struct contiguous_iterator : public base_contiguous_iterator<T, Container> {
+    // Alias for the base class.
+    using base_type = base_contiguous_iterator<T, Container>;
+    // Alias for types from the base class.
+    using typename base_type::difference_type;
+    using typename base_type::iterator_category;
+    using typename base_type::iterator_concept;
+    using typename base_type::pointer;
+    using typename base_type::reference;
+    using typename base_type::value_type;
+
+    // Default constructor.
+    contiguous_iterator() noexcept : m_current() {}
+
+    // Pointer to iterator constructor.
+    contiguous_iterator(pointer it) noexcept : m_current(it) {}
+
+    // As per P2727R4, for contiguous iterator we only need to provide operator*, operator+= and operator-.
+    reference operator*() const noexcept { return *m_current; }
+    auto&     operator+=(difference_type pos) noexcept {
+        m_current += pos;
+        return *this;
+    }
+    difference_type operator-(contiguous_iterator other) const noexcept { return m_current - other.m_current; }
+
+  private:
+    T* m_current;
+};
+
+// Check concepts for the contiguous_iterator class.
+// Test here with Container=int[]/const int[]. More tests can be found in iterator.t.cpp.
+static_assert(std::contiguous_iterator<contiguous_iterator<int, int[]>>);
+static_assert(std::contiguous_iterator<contiguous_iterator<const int, const int[]>>);
+
+} // namespace beman::optional::detail
+
+#endif // BEMAN_OPTIONAL26_DETAIL_ITERATOR_HPP

include/Beman/Optional26/detail/stl_interfaces/config.hpp

@@ -0,0 +1,49 @@
+// include/Beman/Optional26/detail/stl_interfaces/config.hpp -*-C++-*-
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+// Copyright (C) 2020 T. Zachary Laine
+//
+// Distributed under the Boost Software License, Version 1.0. (See
+// accompanying file LICENSE_1_0.txt or copy at
+// http://www.boost.org/LICENSE_1_0.txt)
+#ifndef BEMAN_OPTIONAL26_DETAIL_STL_INTERFACES_CONFIG_HPP
+#define BEMAN_OPTIONAL26_DETAIL_STL_INTERFACES_CONFIG_HPP
+
+// Included for definition of __cpp_lib_concepts.
+#include <iterator>
+
+#if defined(__cpp_lib_concepts) && defined(__cpp_lib_ranges) && \
+    !defined(BEMAN_OPTIONAL26_DETAIL_STL_INTERFACES_DISABLE_CONCEPTS)
+#define BEMAN_OPTIONAL26_DETAIL_STL_INTERFACES_USE_CONCEPTS 1
+#else
+#define BEMAN_OPTIONAL26_DETAIL_STL_INTERFACES_USE_CONCEPTS 0
+#endif
+
+#if defined(__cpp_explicit_this_parameter) && BEMAN_OPTIONAL26_DETAIL_STL_INTERFACES_USE_CONCEPTS && \
+    !defined(BEMAN_OPTIONAL26_DETAIL_STL_INTERFACES_DISABLE_DEDUCED_THIS)
+#define BEMAN_OPTIONAL26_DETAIL_STL_INTERFACES_USE_DEDUCED_THIS 1
+#else
+#define BEMAN_OPTIONAL26_DETAIL_STL_INTERFACES_USE_DEDUCED_THIS 0
+#endif
+
+// The inline namespaces v1, v2, and v3 represent C++14, C++20, and C++23 and
+// later, respectively.  v1 is inline for standards before C++20, and v2 is
+// inline for C++20 and later.  Note that this only applies to code for which
+// multiple vI namespace alternatives exist.  For example, some instances of
+// the v1 namespace may still be inline, if there is no v2 version of its
+// contents.
+#if !BEMAN_OPTIONAL26_DETAIL_STL_INTERFACES_USE_CONCEPTS && !BEMAN_OPTIONAL26_DETAIL_STL_INTERFACES_USE_DEDUCED_THIS
+#define BEMAN_OPTIONAL26_DETAIL_STL_INTERFACES_NAMESPACE_V1 inline namespace v1
+#define BEMAN_OPTIONAL26_DETAIL_STL_INTERFACES_NAMESPACE_V2 namespace v2
+#define BEMAN_OPTIONAL26_DETAIL_STL_INTERFACES_NAMESPACE_V3 namespace v3
+#elif BEMAN_OPTIONAL26_DETAIL_STL_INTERFACES_USE_CONCEPTS && !BEMAN_OPTIONAL26_DETAIL_STL_INTERFACES_USE_DEDUCED_THIS
+#define BEMAN_OPTIONAL26_DETAIL_STL_INTERFACES_NAMESPACE_V1 namespace v1
+#define BEMAN_OPTIONAL26_DETAIL_STL_INTERFACES_NAMESPACE_V2 inline namespace v2
+#define BEMAN_OPTIONAL26_DETAIL_STL_INTERFACES_NAMESPACE_V3 namespace v3
+#else
+#define BEMAN_OPTIONAL26_DETAIL_STL_INTERFACES_NAMESPACE_V1 namespace v1
+#define BEMAN_OPTIONAL26_DETAIL_STL_INTERFACES_NAMESPACE_V2 namespace v2
+#define BEMAN_OPTIONAL26_DETAIL_STL_INTERFACES_NAMESPACE_V3 inline namespace v3
+#endif
+
+#endif

include/Beman/Optional26/detail/stl_interfaces/fwd.hpp

@@ -0,0 +1,88 @@
+// include/Beman/Optional26/detail/stl_interfaces/fwd.hpp -*-C++-*-
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+// Copyright (C) 2019 T. Zachary Laine
+//
+// Distributed under the Boost Software License, Version 1.0. (See
+// accompanying file LICENSE_1_0.txt or copy at
+// http://www.boost.org/LICENSE_1_0.txt)
+#ifndef BEMAN_OPTIONAL26_DETAIL_STL_INTERFACES_FWD_HPP
+#define BEMAN_OPTIONAL26_DETAIL_STL_INTERFACES_FWD_HPP
+
+#include <Beman/Optional26/detail/stl_interfaces/config.hpp>
+
+#if BEMAN_OPTIONAL26_DETAIL_STL_INTERFACES_USE_CONCEPTS
+#include <ranges>
+#endif
+#if defined(__cpp_lib_three_way_comparison)
+#include <compare>
+#endif
+
+#ifndef BEMAN_OPTIONAL26_DETAIL_STL_INTERFACES_DOXYGEN
+
+#if defined(_MSC_VER) || defined(__GNUC__) && __GNUC__ < 8
+#define BEMAN_OPTIONAL26_DETAIL_STL_INTERFACES_NO_HIDDEN_FRIEND_CONSTEXPR
+#define BEMAN_OPTIONAL26_DETAIL_STL_INTERFACES_HIDDEN_FRIEND_CONSTEXPR
+#else
+#define BEMAN_OPTIONAL26_DETAIL_STL_INTERFACES_HIDDEN_FRIEND_CONSTEXPR constexpr
+#endif
+
+#if defined(__GNUC__) && __GNUC__ < 9
+#define BEMAN_OPTIONAL26_DETAIL_STL_INTERFACES_CONCEPT concept bool
+#else
+#define BEMAN_OPTIONAL26_DETAIL_STL_INTERFACES_CONCEPT concept
+#endif
+
+#endif
+
+namespace beman::optional::detail {
+namespace stl_interfaces {
+
+/** An enumeration used to indicate whether the underlying data have a
+    contiguous or discontiguous layout when instantiating `view_interface`
+    and `sequence_container_interface`. */
+enum class element_layout : bool { discontiguous = false, contiguous = true };
+
+BEMAN_OPTIONAL26_DETAIL_STL_INTERFACES_NAMESPACE_V1 {
+
+    namespace v1_dtl {
+    template <typename... T>
+    using void_t = void;
+
+    template <typename Iter>
+    using iter_difference_t = typename std::iterator_traits<Iter>::difference_type;
+
+    template <typename Range, typename = void>
+    struct iterator;
+    template <typename Range>
+    struct iterator<Range, void_t<decltype(std::declval<Range&>().begin())>> {
+        using type = decltype(std::declval<Range&>().begin());
+    };
+    template <typename Range>
+    using iterator_t = typename iterator<Range>::type;
+
+    template <typename Range, typename = void>
+    struct sentinel;
+    template <typename Range>
+    struct sentinel<Range, void_t<decltype(std::declval<Range&>().end())>> {
+        using type = decltype(std::declval<Range&>().end());
+    };
+    template <typename Range>
+    using sentinel_t = typename sentinel<Range>::type;
+
+    template <typename Range>
+    using range_difference_t = iter_difference_t<iterator_t<Range>>;
+
+    template <typename Range>
+    using common_range = std::is_same<iterator_t<Range>, sentinel_t<Range>>;
+
+    template <typename Range, typename = void>
+    struct decrementable_sentinel : std::false_type {};
+    template <typename Range>
+    struct decrementable_sentinel<Range, void_t<decltype(--std::declval<sentinel_t<Range>&>())>> : std::true_type {};
+    } // namespace v1_dtl
+}
+} // namespace stl_interfaces
+} // namespace beman::optional::detail
+
+#endif