diff --git a/src/content/docs/cpp/language/named_req/DefaultConstructible.mdx b/src/content/docs/cpp/language/named_req/DefaultConstructible.mdx
new file mode 100644
index 00000000..3c650e59
--- /dev/null
+++ b/src/content/docs/cpp/language/named_req/DefaultConstructible.mdx
@@ -0,0 +1,91 @@
+---
+title: "C++ named requirements: DefaultConstructible"
+cppdoc:
+ revision:
+ since: C++11
+---
+
+import { DR, DRList } from "@components/defect-report";
+import { Desc, DescList } from "@components/desc-list";
+
+Specifies that an instance of the type can be default constructed.
+
+
+## Requirements
+The type `T` satisfies _DefaultConstructible_ if all following statements and expressions are valid and have their specified effects:
+
+Given
+
+- `u`, an expression of type `T`.
+
+- `u`, an lvalue expression of type `Key`.
+
+|Expression/Statement| Postcondition|
+|---|---|
+|`T u;`| The object `u` is default-initialized.|
+|`T u{};`| The object `u` is value-initialized or aggregate-initialized.|
+|`T()`| All resources owned by `u` are reclaimed, no exceptions are thrown.|
+|`T{}`| A temporary object of type `T` is value-initialized or aggregate-initialized.|
+
+## Notes
+
+For objects of non-aggregate class type, a public default constructor must be defined (either user-defined or implicitly defined) to satisfy _DefaultConstructible_.
+
+Non-const objects of non-class object type are always _DefaultConstructible_.
+
+Const non-class types are not _DefaultConstructible_.
+
+Const aggregate types are not _DefaultConstructible_ if any of their members is an object of non-class type.
+
+Non-object types (function types, reference types, and the (possibly cv-qualified) type void) as well as the const non-object types are never _DefaultConstructible_.
+
+# Defect reports
+
+The following behavior-changing defect reports were applied retroactively to previously published C++ standards.
+
+
+
+
+ the requirements of _DefaultConstructible_ were missing
+
+
+ added
+
+
+
+
+ initialzing an object of a _DefaultConstructible_ type with an
+empty initializer could only result in value-initialization
+
+
+ can also lead to aggregate-initialization
+
+
+
+## See also
+
+
+
+
+
+ `std::is_default_constructible`
+
+
+ `std::is_trivially_default_constructible`
+
+
+ `std::is_nothrow_default_constructible`
+
+
+ checks if a type has a default constructor
+
+
+
+
+ `default_initializable`
+
+
+ specifies that an object of a type can be default constructed
+
+
+
diff --git a/src/content/docs/cpp/language/named_req/Destructible.mdx b/src/content/docs/cpp/language/named_req/Destructible.mdx
new file mode 100644
index 00000000..71db9125
--- /dev/null
+++ b/src/content/docs/cpp/language/named_req/Destructible.mdx
@@ -0,0 +1,60 @@
+---
+title: "C++ named requirements: Destructible"
+cppdoc:
+ revision:
+ since: C++11
+---
+
+import { DR, DRList } from "@components/defect-report";
+import { Desc, DescList } from "@components/desc-list";
+
+Specifies that an instance of the type can be destructed.
+
+
+## Requirements
+The type `T` satisfies `Destructible` if
+
+Given
+
+- `u`, an expression of type `T`.
+
+- `u`, an lvalue expression of type `Key`.
+
+|Expression| Post-Conditions|
+|---|---|
+|`u.~T()`| All resources owned by `u` are reclaimed, no exceptions are thrown.|
+
+## Notes
+
+
+Destructors are called implicitly at the end of object lifetime such as when leaving scope or by the delete-expression. Explicit destructor call as shown in the type requirement table is rare.
+
+Thanks to pseudo destructor call, all scalar types meet the requirement of Destructible, while array types and reference types do not. Note that `std::is_destructible` allows arrays and reference types.
+
+## See also
+
+
+
+
+
+ `std::is_destructible`
+
+
+ `std::is_trivially_destructible`
+
+
+ `std::is_nothrow_destructible`
+
+
+ checks if a type has a non-deleted destructor
+
+
+
+
+ `destructible`
+
+
+ specifies that an object of the type can be destroyed
+
+
+
diff --git a/src/content/docs/cpp/language/named_req/Hash.mdx b/src/content/docs/cpp/language/named_req/Hash.mdx
new file mode 100644
index 00000000..dfb8c6cc
--- /dev/null
+++ b/src/content/docs/cpp/language/named_req/Hash.mdx
@@ -0,0 +1,58 @@
+---
+title: "C++ named requirements: Hash"
+cppdoc:
+ revision:
+ since: C++11
+---
+
+import { DR, DRList } from "@components/defect-report";
+import { Desc, DescList } from "@components/desc-list";
+
+A ***Hash*** is a function object for which the output depends only on the input and has a very low probability of yielding the same output given different input values.
+
+
+## Requirements
+The type `T` satisfies `Hash` if
+
+The type `T` satisfies `FunctionObject`, `CopyConstructible`, `Destructible`, and
+Given
+
+- `h`, a value of type `T` or const `T`, whose argument type is `Key`,
+- `k`, a value of type convertible to `Key` or `const Key`,
+- `u`, an lvalue expression of type `Key`.
+
+The following expressions must be valid and have their specified effects.
+
+|Expression| Return type| Requirements|
+|---|---|---|
+|`h(k)`| `std::size_t`|The returned value depends only on the value of `k` for the duration of the program.
All evaluations of `h(k)` executed within a given execution of a program yield the same result for the same value of `k`.
The probability of `h(a) == h(b)` for `a != b` should approach `1.0 / std::numeric_limits::max()`.|
+|`h(u)` | `std::size_t` | `u` is not modified.|
+
+## Standard Library
+
+
+
+
+
+ `hash`
+
+
+ hash function object
+
+
+
+# Defect reports
+
+The following behavior-changing defect reports were applied retroactively to previously published C++ standards.
+
+
+
+
+ same results for same arguments were required in all cases
+
+
+ only required within a single execution
+
+
+
+
diff --git a/src/content/docs/cpp/language/named_req/_meta.yml b/src/content/docs/cpp/language/named_req/_meta.yml
new file mode 100644
index 00000000..7668e33f
--- /dev/null
+++ b/src/content/docs/cpp/language/named_req/_meta.yml
@@ -0,0 +1 @@
+label: Name Requirements
diff --git a/src/content/docs/cpp/library/utility/hash.mdx b/src/content/docs/cpp/library/utility/hash.mdx
new file mode 100644
index 00000000..fa7f102a
--- /dev/null
+++ b/src/content/docs/cpp/library/utility/hash.mdx
@@ -0,0 +1,232 @@
+---
+title: std::hash
+cppdoc:
+ revision:
+ since: C++11
+---
+
+import { CppHeader } from "@components/header";
+import { Decl, DeclDoc } from "@components/decl-doc";
+import { Desc, DescList } from "@components/desc-list";
+import Missing from "@components/Missing.astro";
+import { ParamDoc, ParamDocList } from "@components/param-doc";
+import { Revision, RevisionBlock } from "@components/revision";
+import DocLink from "@components/DocLink.astro"
+import { Card } from "@astrojs/starlight/components";
+import FlexTable from "@components/FlexTable.astro";
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+ ```cpp
+ template
+ struct hash;
+ ```
+
+
+
+ The unordered associative containers `std::unordered_set`, `std::unordered_multiset`, `std::unordered_map`, `std::unordered_multimap` use specializations of the template std::hash as the default hash function.
+
+
+Given a type `Key`, each specialization `std::hash` is either _enabled_ or _disabled_ :
+
+- If `std::hash` is not provided by the program or the user, it is disabled.
+- Otherwise, `std::hash` is enabled if all following conditions are satisfied:
+ - All following requirements are satisfied:
+ - `Hash` (with `Key` as the function call argument type)
+ - `DefaultConstructible`
+ - [CopyAssignable](../named_req/CopyAssignable.html "cpp/named req/CopyAssignable")
+ - [Swappable](../named_req/Swappable.html "cpp/named req/Swappable")
+
+ - Given the following values:
+ - `h`, an object of type `std::hash`.
+ - `k1` and `k2`, objects of type `Key`.
+ All following requirements are satisfied:
+ - If `k1 == k2` is true, `h(k1) == h(k2)` is also true.
+ - Unless `std::hash` is a [program-defined specialization](../language/type-id.html#Program-defined_type "cpp/language/type"), h(k1) will never throw an exception.
+
+- Otherwise, `std::hash` is disabled.
+
+Disabled specializations do not satisfy `Hash` , do not satisfy [FunctionObject](../named_req/FunctionObject.html "cpp/named req/FunctionObject"), and following values are all false:
+
+- `std::is_default_constructible>::value`
+- `std::is_copy_constructible>::value`
+- `std::is_move_constructible>::value`
+- `std::is_copy_assignable>::value`
+- `std::is_move_assignable>::value`
+
+In other words, they exist, but cannot be used.
+
+
+
+ Nested types:
+ |Name|Definition|
+ |---|---|
+ |`argument_type` (deprecared in C++ 17)| `Key`|
+ |`result_type` (deprecared in C++ 17)| `size_t`|
+
+
+
+
+### Member functions
+| | |
+|---|---|
+|(constuctor) | constructs a hash function object |
+| `operator()` | calculates the hash of the argument |
+
+
+### Standard library specializations
+Each header that declares the template std::hash also provides enabled specializations of std::hash for the following types:
+
+- all cv-unqualified arithmetic types
+- all cv-unqualified enumeration types
+- all cv-unqualified pointer types
+- std::nullptr_t
+
+On top of that, some headers also provide other enabled std::hash specializations for library types (see below).
+
+
+
+
+
+
+ For all std::hash specializations provided by the standard library except the following, all their member functions are noexcept:
+ - `std::hash`
+ - `std::hash`
+ - `std::hash`
+
+
+ - `std::hash`
+ - `std::hash`
+ - `std::hash`
+
+
+
+
+
+
+## Notes
+
+The actual hash functions are implementation-dependent and are not required to fulfill any other quality criteria except those specified above. Notably, some implementations use trivial (identity) hash functions which map an integer to itself. In other words, these hash functions are designed to work with unordered associative containers, but not as cryptographic hashes, for example.
+
+Hash functions are only required to produce the same result for the same input within a single execution of a program; this allows salted hashes that prevent collision denial-of-service attacks.
+
+There is no specialization for C strings. `std::hash` produces a hash of the value of the pointer (the memory address), it does not examine the contents of any character array.
+
+Additional specializations for `std::pair` and the standard container types, as well as utility functions to compose hashes are available in `boost::hash`.
+
+
+## Example
+
+```cpp
+#include
+#include
+#include
+#include
+#include
+#include
+
+struct S
+{
+ std::string first_name;
+ std::string last_name;
+ bool operator==(const S&) const = default; // since C++20
+};
+
+// Before C++20.
+// bool operator==(const S& lhs, const S& rhs)
+// {
+// return lhs.first_name == rhs.first_name && lhs.last_name == rhs.last_name;
+// }
+
+// Custom hash can be a standalone function object.
+struct MyHash
+{
+ std::size_t operator()(const S& s) const noexcept
+ {
+ std::size_t h1 = std::hash{}(s.first_name);
+ std::size_t h2 = std::hash{}(s.last_name);
+ return h1 ^ (h2 << 1); // or use boost::hash_combine
+ }
+};
+
+// Custom specialization of std::hash can be injected in namespace std.
+template<>
+struct std::hash
+{
+ std::size_t operator()(const S& s) const noexcept
+ {
+ std::size_t h1 = std::hash{}(s.first_name);
+ std::size_t h2 = std::hash{}(s.last_name);
+ return h1 ^ (h2 << 1); // or use boost::hash_combine
+ }
+};
+
+int main()
+{
+ std::string str = "Meet the new boss...";
+ std::size_t str_hash = std::hash{}(str);
+ std::cout << "hash(" << std::quoted(str) << ") =\t" << str_hash << '\n';
+
+ S obj = {"Hubert", "Farnsworth"};
+ // Using the standalone function object.
+ std::cout << "hash(" << std::quoted(obj.first_name) << ", "
+ << std::quoted(obj.last_name) << ") =\t"
+ << MyHash{}(obj) << " (using MyHash) or\n\t\t\t\t"
+ << std::hash{}(obj) << " (using injected specialization)\n";
+
+ // Custom hash makes it possible to use custom types in unordered containers.
+ // The example will use the injected std::hash specialization above,
+ // to use MyHash instead, pass it as a second template argument.
+ std::unordered_set names = {obj, {"Bender", "Rodriguez"}, {"Turanga", "Leela"}};
+ for (auto const& s: names)
+ std::cout << std::quoted(s.first_name) << ' '
+ << std::quoted(s.last_name) << '\n';
+}
+```
+
+Possible outputs:
+
+```cpp
+hash("Meet the new boss...") = 10656026664466977650
+hash("Hubert", "Farnsworth") = 12922914235676820612 (using MyHash) or
+ 12922914235676820612 (using injected specialization)
+"Bender" "Rodriguez"
+"Turanga" "Leela"
+"Hubert" "Farnsworth"
+```
+
+## Defect reports
+
+The following behavior-changing defect reports were applied retroactively to previously published C++ standards.
+
+| DR | Applied to | Behavior as published | Correct behavior |
+| --- | --- | --- | --- |
+| [LWG 2119](https://cplusplus.github.io/LWG/issue2119) | C++11 | specializations for extended integer types were missing | provided |
+| [LWG 2148](https://cplusplus.github.io/LWG/issue2148) | C++11 | specializations for enumerations were missing | provided |
+| [LWG 2543](https://cplusplus.github.io/LWG/issue2543) | C++11 | `std::hash` might not be SFINAE-friendly | made SFINAE-friendly |
+| [LWG 2817](https://cplusplus.github.io/LWG/issue2817) | C++11 | specialization for [std::nullptr\_t](../types/nullptr_t.html "cpp/types/nullptr_t") was missing | provided |
+
diff --git a/src/content/docs/cpp/library/utility/hash/operator-call.mdx b/src/content/docs/cpp/library/utility/hash/operator-call.mdx
new file mode 100644
index 00000000..b005a4c8
--- /dev/null
+++ b/src/content/docs/cpp/library/utility/hash/operator-call.mdx
@@ -0,0 +1,83 @@
+---
+title: std::hash::operator()
+cppdoc:
+ revision:
+ since: C++11
+---
+
+import { ParamDoc, ParamDocList } from "@components/param-doc";
+
+Specializations of `std::hash` should define an `operator()` that:
+
+- Takes a single argument key of type `Key`.
+- Returns a value of type `std::size_t` that represents the hash value of key.
+- For two parameters `k1` and `k2` that are equal, `std::hash()(k1) == std::hash()(k2)`.
+- For two different parameters `k1` and `k2` that are not equal, the probability that `std::hash()(k1) == std::hash()(k2)` should be very small, approaching `1.0 / std::numeric_limits::max()`.
+
+
+## Parameters
+
+
+ the object to be hashed
+
+
+
+## Return value
+A `std::size_t` representing the hash value.
+
+## Exceptions
+Hash functions should not throw exceptions.
+
+## Example
+The following code shows how to specialize the std::hash template for a custom class. The hash function uses Fowler–Noll–Vo hash algorithm.
+
+```cpp
+#include
+#include
+#include
+#include
+
+struct Employee
+{
+ std::string name;
+ std::uint64_t ID;
+};
+
+namespace std
+{
+ template <>
+ class hash
+ {
+ public:
+ std::uint64_t operator()(const Employee& employee) const
+ {
+ // computes the hash of an employee using a variant
+ // of the Fowler-Noll-Vo hash function
+ constexpr std::uint64_t prime{0x100000001B3};
+ std::uint64_t result{0xcbf29ce484222325};
+
+ for (std::uint64_t i{}, ie = employee.name.size(); i != ie; ++i)
+ result = (result * prime) ^ employee.name[i];
+
+ return result ^ (employee.ID << 1);
+ }
+ };
+}
+
+int main()
+{
+ Employee employee;
+ employee.name = "Zaphod Beeblebrox";
+ employee.ID = 42;
+
+ std::hash hash_fn;
+ std::cout << hash_fn(employee) << '\n';
+}
+```
+
+Output:
+
+```cpp
+12615575401975788567
+```
+