maybe-constの解説を追加

Author: tetsurom

GLOBAL_QUALIFY_LIST.txt

@@ -77,6 +77,7 @@
 * <complex>[link /reference/complex.md]
 * <concepts>[link /reference/concepts.md]
     * common_reference_with[link /reference/concepts/common_reference_with.md]
+    * common_type_t[link /reference/concepts/common_type.md]
     * common_with[link /reference/concepts/common_with.md]
     * copy_constructible[link /reference/concepts/copy_constructible.md]
     * invocable[link /reference/concepts/invocable.md]
@@ -198,6 +199,7 @@
     * forward_range[link /reference/ranges/forward_range.md]
     * input_range[link /reference/ranges/input_range.md]
     * iterator_t[link /reference/ranges/iterator_t.md]
+    * maybe-const[link /reference/ranges/maybe-const.md]
     * output_range[link /reference/ranges/output_range.md]
     * random_access_range[link /reference/ranges/random_access_range.md]
     * range_difference_t[link /reference/ranges/range_difference_t.md]
@@ -262,6 +264,7 @@
     * std::tuple[link /reference/tuple/tuple.md]
     * std::tie[link /reference/tuple/tie.md]
 * <type_traits>[link /reference/type_traits.md]
+    * common_reference_t[link /reference/type_traits/common_reference.md]
     * invoke_result_t[link /reference/type_traits/invoke_result.md]
     * is_class_v[link /reference/type_traits/is_class.md]
     * is_object_v[link /reference/type_traits/is_object.md]

reference/exposition-only.md

@@ -48,6 +48,7 @@
 | [`uses-nonqualification-pointer-conversion`](ranges/subrange/uses-nonqualification-pointer-conversion.md) | 直接変換できない型同士のポインタの変換が必要かどうかを表す (concept)                                                    | C++20     |
 | [`convertible-to-non-slicing`](ranges/subrange/convertible-to-non-slicing.md)                             | スライシングを起こさずに変換できるかどうかを表す (concept)                                                                 | C++20     |
 | [`pair-like-convertible-from`](ranges/subrange/pair-like-convertible-from.md)                             | ある2つの型から構築出来る[`pair-like`](tuple/pair-like.md)な型を表す (concept)                                   | C++20     |
+| [`maybe-const`](ranges/maybe-const.md)                                                                    | bool値に応じて`const`修飾を付加する (alias template)                                          | C++23     |
 
 ## `<tuple>`
 

reference/ranges/maybe-const.md

@@ -0,0 +1,22 @@
+# maybe-const
+* ranges[meta header]
+* type-alias[meta id-type]
+* cpp23[meta cpp]
+
+```cpp
+namespace std::ranges {
+  template<bool Const, class T>
+  using maybe-const = conditional_t<Const, const T, T>;
+}
+```
+
+## 概要
+
+`maybe-const<Const, T>` は、bool値`Const`が`true`のとき `const T`、`false`のとき`T`となる説明専用の型エイリアスである。
+
+## バージョン
+### 言語
+- C++23
+
+## 参照
+- [N4950 26 Ranges library](https://timsong-cpp.github.io/cppwp/n4950/ranges)