Updated readme and synopsis to reflect wording in P3411R2

Author: patrickroberts

.markdownlint.yaml

@@ -9,3 +9,4 @@ MD033: false
 # Update the comment in .clang-format if we no-longer tie these two column limits.
 MD013:
   line_length: 119
+  code_blocks: false

README.md

@@ -4,14 +4,26 @@ SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
 # beman.any_view: A generalized type-erased view with customizable properties
 
-![Library Status](https://github.com/bemanproject/beman/blob/c6997986557ec6dda98acbdf502082cdf7335526/images/badges/beman_badge-beman_library_under_development.svg)
+![Library Status](https://raw.githubusercontent.com/bemanproject/beman/refs/heads/main/images/badges/beman_badge-beman_library_under_development.svg)
 ![Continuous Integration Tests](https://github.com/bemanproject/any_view/actions/workflows/ci_tests.yml/badge.svg)
 ![Lint Check (pre-commit)](https://github.com/bemanproject/any_view/actions/workflows/pre-commit.yml/badge.svg)
 
-**Implements**: `std::ranges::any_view` proposed in [any_view (P3411R2)](https://huixie90.github.io/cpp_papers/generated/any_view).
+**Implements**: `std::ranges::any_view` proposed in [any_view (P3411R2)](https://wg21.link/p3411r2).
 
 **Status**: [Under development and not yet ready for production use.](https://github.com/bemanproject/beman/blob/main/docs/BEMAN_LIBRARY_MATURITY_MODEL.md#under-development-and-not-yet-ready-for-production-use)
 
+**Featured**: [C++Now 2025](https://schedule.cppnow.org/wp-content/uploads/2025/03/A-View-for-Any-Occasion.pdf)
+
+## Motivation
+
+`any_view` equips library APIs with the ability to declare function parameters and return types as views, while
+de-coupling the interface from an implementation that can fully leverage the power of C++20 ranges. By using
+type-erased views, the library can be compiled separately.
+
+As a return type, `any_view` grants a library author the freedom to change how the function is implemented to return
+the view without modifying its interface. As a parameter type, it allows users to call the library function with any
+range as an argument that can be consumed directly, rather than copying it into some bespoke, library-specific type.
+
 ## Usage
 
 ```cpp
@@ -64,10 +76,11 @@ For CMake based projects, you can include it as a dependency using the `FetchCon
 include(FetchContent)
 
 FetchContent_Declare(
-  beman.any_view
-  GIT_REPOSITORY https://github.com/bemanproject/any_view.git
-  GIT_TAG main
-  EXCLUDE_FROM_ALL)
+    beman.any_view
+    GIT_REPOSITORY https://github.com/bemanproject/any_view.git
+    GIT_TAG main
+    EXCLUDE_FROM_ALL
+)
 FetchContent_MakeAvailable(beman.any_view)
 ```
 
@@ -88,6 +101,7 @@ target_link_libraries(yourlib PUBLIC beman::any_view)
 ```cpp
 namespace beman::any_view {
 
+// [range.any]
 enum class any_view_options {
     input         = 0b00000001,
     forward       = 0b00000011,
@@ -99,22 +113,24 @@ enum class any_view_options {
     copyable      = 0b10000000,
 };
 
-constexpr any_view_options operator|(any_view_options l, any_view_options r) noexcept;
-constexpr any_view_options operator&(any_view_options l, any_view_options r) noexcept;
-constexpr any_view_options operator^(any_view_options l, any_view_options r) noexcept;
+constexpr any_view_options operator|(any_view_options, any_view_options) noexcept;
+constexpr any_view_options operator&(any_view_options, any_view_options) noexcept;
 
-constexpr any_view_options operator~(any_view_options o) noexcept;
+template <class T>
+struct /*rvalue-ref*/ {
+    using type = T;
+};
 
-constexpr any_view_options& operator|=(any_view_options& l, any_view_options r) noexcept;
-constexpr any_view_options& operator&=(any_view_options& l, any_view_options r) noexcept;
-constexpr any_view_options& operator^=(any_view_options& l, any_view_options r) noexcept;
+template <class T>
+struct /*rvalue-ref*/<T&> {
+    using type = T&&;
+};
 
-template <class T> struct /*as-rvalue*/ { using type = T; };
-template <class T> struct /*as-rvalue*/<T&> { using type = T&&; };
-template <class T> using /*as-rvalue-t*/ = /*as-rvalue*/<T>::type;
+template <class T>
+using /*rvalue-ref-t*/ = /*rvalue-ref*/<T>::type;
 
 template <class RangeT, class AnyViewT>
-concept ext_any_compatible_viewable_range = /* see description */;
+concept ext_any_compatible_viewable_range = /* ... */;
 
 template <class ElementT,
           any_view_options OptsV = any_view_options::input,
@@ -125,30 +141,29 @@ class any_view : public std::ranges::view_interface<any_view<ElementT, OptsV, Re
     class iterator; // exposition-only
     class sentinel; // exposition-only
 
-    using size_type = std::make_unsigned_t<DiffT>; // exposition-only
-
   public:
+    // [range.any.ctor]
     template <class RangeT>
-        requires(not std::same_as<std::remove_cvref_t<RangeT>, any_view> and
-                 ext_any_compatible_viewable_range<RangeT, any_view>)
     constexpr any_view(RangeT&& range);
-
-    constexpr any_view(const any_view&)
-        requires(bool(OptsV & any_view_options::copyable));
-
+    constexpr any_view(const any_view&);
     constexpr any_view(any_view&&) noexcept;
 
-    constexpr any_view& operator=(const any_view&)
-        requires(bool(OptsV & any_view_options::copyable));
-
+    constexpr any_view& operator=(const any_view&);
     constexpr any_view& operator=(any_view&&) noexcept;
 
+    constexpr ~any_view();
+
+    // [range.any.access]
     constexpr iterator begin();
 
     constexpr sentinel end();
 
-    constexpr size_type size() const
-        requires(bool(OptsV & any_view_options::sized));
+    constexpr std::make_unsigned_t<DiffT> size() const;
+
+    // [range.any.swap]
+    constexpr void swap(any_view&) noexcept;
+
+    constexpr friend void swap(any_view&, any_view&) noexcept;
 };
 
 } // namespace beman::any_view
@@ -267,6 +282,74 @@ Total Test time (real) =   0.15 sec
 
 </details>
 
+## Performance
+
+Various benchmarks are available to build and run using the CMake target `beman.any_view.benchmarks`.
+
+<details>
+<summary>Example output comparing <code>reserved</code> to <code>fused</code> for <code>beman.any_view.benchmarks.all</code></summary>
+
+```text
++ cmake --build build --config Release --target beman.any_view.benchmarks.all
+[27/27] Linking CXX executable tests/beman/any_view/beman.any_view.benchmarks.all
++ build/_deps/benchmark-src/tools/compare.py benchmarksfiltered build/tests/beman/any_view/beman.any_view.benchmarks.all reserved build/tests/beman/any_view/beman.any_view.benchmarks.all fused
+RUNNING: build/tests/beman/any_view/beman.any_view.benchmarks.all --benchmark_filter=reserved
+Run on (32 X 2419.2 MHz CPU s)
+CPU Caches:
+  L1 Data 48 KiB (x16)
+  L1 Instruction 32 KiB (x16)
+  L2 Unified 2048 KiB (x16)
+  L3 Unified 36864 KiB (x1)
+Load Average: 0.25, 0.17, 0.11
+-----------------------------------------------------------------
+Benchmark                       Time             CPU   Iterations
+-----------------------------------------------------------------
+BM_all_reserved/1024         1783 ns         1783 ns       389936
+BM_all_reserved/2048         3839 ns         3839 ns       191729
+BM_all_reserved/4096         7067 ns         7067 ns        89826
+BM_all_reserved/8192        14756 ns        14756 ns        48245
+BM_all_reserved/16384       30317 ns        30317 ns        23191
+BM_all_reserved/32768       73651 ns        73650 ns         9626
+BM_all_reserved/65536      215342 ns       215341 ns         3413
+BM_all_reserved/131072     424794 ns       424793 ns         1654
+BM_all_reserved/262144     887833 ns       887828 ns          789
+RUNNING: build/tests/beman/any_view/beman.any_view.benchmarks.all --benchmark_filter=fused
+Run on (32 X 2419.2 MHz CPU s)
+CPU Caches:
+  L1 Data 48 KiB (x16)
+  L1 Instruction 32 KiB (x16)
+  L2 Unified 2048 KiB (x16)
+  L3 Unified 36864 KiB (x1)
+Load Average: 0.31, 0.19, 0.11
+--------------------------------------------------------------
+Benchmark                    Time             CPU   Iterations
+--------------------------------------------------------------
+BM_all_fused/1024         1660 ns         1660 ns       437469
+BM_all_fused/2048         3219 ns         3219 ns       210096
+BM_all_fused/4096         7100 ns         7100 ns       100823
+BM_all_fused/8192        15088 ns        15088 ns        45117
+BM_all_fused/16384       33719 ns        33719 ns        21827
+BM_all_fused/32768       72098 ns        72097 ns         9582
+BM_all_fused/65536      150699 ns       150698 ns         4629
+BM_all_fused/131072     316431 ns       316430 ns         2234
+BM_all_fused/262144     583499 ns       583500 ns         1091
+Comparing reserved (from build/tests/beman/any_view/beman.any_view.benchmarks.all) to fused (from build/tests/beman/any_view/beman.any_view.benchmarks.all)
+Benchmark                                            Time             CPU      Time Old      Time New       CPU Old       CPU New
+---------------------------------------------------------------------------------------------------------------------------------
+BM_all_[reserved vs. fused]/1024                  -0.0689         -0.0689          1783          1660          1783          1660
+BM_all_[reserved vs. fused]/2048                  -0.1615         -0.1615          3839          3219          3839          3219
+BM_all_[reserved vs. fused]/4096                  +0.0047         +0.0047          7067          7100          7067          7100
+BM_all_[reserved vs. fused]/8192                  +0.0225         +0.0225         14756         15088         14756         15088
+BM_all_[reserved vs. fused]/16384                 +0.1122         +0.1122         30317         33719         30317         33719
+BM_all_[reserved vs. fused]/32768                 -0.0211         -0.0211         73651         72098         73650         72097
+BM_all_[reserved vs. fused]/65536                 -0.3002         -0.3002        215342        150699        215341        150698
+BM_all_[reserved vs. fused]/131072                -0.2551         -0.2551        424794        316431        424793        316430
+BM_all_[reserved vs. fused]/262144                -0.3428         -0.3428        887833        583499        887828        583500
+OVERALL_GEOMEAN                                   -0.1255         -0.1255
+```
+
+</details>
+
 ## Contributing
 
 Please do! Issues and pull requests are appreciated.

include/beman/any_view/any_view.hpp

@@ -10,10 +10,10 @@ namespace beman::any_view {
 template <class ElementT,
           any_view_options OptsV = any_view_options::input,
           class RefT             = ElementT&,
-          class RValueRefT       = detail::as_rvalue_t<RefT>,
+          class RValueRefT       = detail::rvalue_ref_t<RefT>,
           class DiffT            = std::ptrdiff_t>
 class any_view : public std::ranges::view_interface<any_view<ElementT, OptsV, RefT, RValueRefT, DiffT>> {
-    static_assert((OptsV & any_view_options::input) == any_view_options::input, "any_view must model input_range");
+    static_assert(bool(OptsV & any_view_options::input), "any_view must model input_range");
 
     using iterator_concept = decltype(detail::get_iter_concept<OptsV>());
     using iterator         = detail::any_iterator<iterator_concept, ElementT, RefT, RValueRefT, DiffT>;
@@ -31,6 +31,7 @@ class any_view : public std::ranges::view_interface<any_view<ElementT, OptsV, Re
     }
 
   public:
+    // [range.any.ctor]
     template <class RangeT>
         requires(not std::same_as<std::remove_cvref_t<RangeT>, any_view> and
                  ext_any_compatible_viewable_range<RangeT, any_view>)
@@ -49,6 +50,9 @@ class any_view : public std::ranges::view_interface<any_view<ElementT, OptsV, Re
 
     constexpr any_view& operator=(any_view&&) noexcept = default;
 
+    constexpr ~any_view() = default;
+
+    // [range.any.access]
     [[nodiscard]] constexpr iterator begin() { return view_ptr->begin(); }
 
     [[nodiscard]] constexpr sentinel end() { return std::default_sentinel; }
@@ -58,6 +62,11 @@ class any_view : public std::ranges::view_interface<any_view<ElementT, OptsV, Re
     {
         return view_ptr->size();
     }
+
+    // [range.any.swap]
+    constexpr void swap(any_view& other) noexcept { std::swap(view_ptr, other.view_ptr); }
+
+    constexpr friend void swap(any_view& lhs, any_view& rhs) noexcept { return lhs.swap(rhs); }
 };
 
 } // namespace beman::any_view

include/beman/any_view/any_view_options.hpp

@@ -24,20 +24,6 @@ enum class any_view_options {
     return any_view_options(static_cast<int>(l) & static_cast<int>(r));
 }
 
-[[nodiscard]] constexpr any_view_options operator^(any_view_options l, any_view_options r) noexcept {
-    return any_view_options(static_cast<int>(l) ^ static_cast<int>(r));
-}
-
-[[nodiscard]] constexpr any_view_options operator~(any_view_options o) noexcept {
-    return any_view_options(~static_cast<int>(o));
-}
-
-constexpr any_view_options& operator|=(any_view_options& l, any_view_options r) noexcept { return l = l | r; }
-
-constexpr any_view_options& operator&=(any_view_options& l, any_view_options r) noexcept { return l = l & r; }
-
-constexpr any_view_options& operator^=(any_view_options& l, any_view_options r) noexcept { return l = l ^ r; }
-
 } // namespace beman::any_view
 
 #endif // BEMAN_ANY_VIEW_ANY_VIEW_OPTIONS_HPP

include/beman/any_view/detail/type_traits.hpp

@@ -10,13 +10,13 @@
 namespace beman::any_view::detail {
 
 template <class T>
-struct as_rvalue : std::type_identity<T> {};
+struct rvalue_ref : std::type_identity<T> {};
 
 template <class T>
-struct as_rvalue<T&> : std::type_identity<T&&> {};
+struct rvalue_ref<T&> : std::type_identity<T&&> {};
 
 template <class T>
-using as_rvalue_t = as_rvalue<T>::type;
+using rvalue_ref_t = rvalue_ref<T>::type;
 
 template <any_view_options OptionsV>
 [[nodiscard]] consteval auto get_iter_concept() {