[#bsl-hash-06]
= xref:bsl.adoc[bsl]::hash
:relfileprefix: ../
:mrdocs:

Empty base class for hashing. This class, and all explicit and partial specializations of this class, shall conform to the C++11 Hash Requirements (C++11 17.6.3.4, [hash.requirements]). Unless this template is explicitly specialized, it will use the default hash algorithm provided by `bslh::Hash<>` to supply hash values. In order to hash a user‐defined type using `bsl::hash`, `bsl::hash` must be explicitly specialized for the type, or, preferably, `hashAppend` must be implemented for the type. For more details on `hashAppend` and `bslh::Hash` see the component `bslh_hash`.

== Synopsis

Declared in `<bslstl_hash.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
template<class TYPE>
struct hash
    : xref:BloombergLP/bslh/Hash-07.adoc[BloombergLP::bslh::Hash<>]
----

== Base Classes

[cols="1,4"]
|===
| Name| Description
| `xref:BloombergLP/bslh/Hash-07.adoc[BloombergLP::bslh::Hash<>]`
| This struct wraps the (template parameter) type `HASH_ALGORITHM` in an interface that satisfies the `hash` requirements of the C++11 standard.
|===

== Type Aliases

[cols="1,4"]
|===
| Name| Description
| xref:BloombergLP/bslh/Hash-02/HashAlgorithm.adoc[`HashAlgorithm`] 
| Make the `HASH_ALGORITHM` template parameter available to clients.
| xref:BloombergLP/bslh/Hash-02/result_type.adoc[`result_type`] 
| The type of the hash value that will be returned by the function‐call operator.
|===


== Member Functions

[cols="1,4"]
|===
| Name| Description
| xref:bsl/hash-06/operator_call-0a.adoc[`operator()`] 
| Function call operators
|===


== Specializations

[cols="1,4"]
|===
| Name| Description
| xref:bsl/hash-0f5.adoc[`hash<bool>`] 
| Specialization of `hash` for `bool` values.
| xref:bsl/hash-0c5.adoc[`hash<char>`] 
| Specialization of `hash` for `char` values.
| xref:bsl/hash-09.adoc[`hash<std::thread::id>`] 
| 
| xref:bsl/hash-0cb.adoc[`hash<int>`] 
| Specialization of `hash` for `int` values.
| xref:bsl/hash-0df.adoc[`hash<long>`] 
| Specialization of `hash` for `long` values.
| xref:bsl/hash-0d8.adoc[`hash<long long>`] 
| Specialization of `hash` for `long long` values.
| xref:bsl/hash-01b.adoc[`hash<short>`] 
| Specialization of `hash` for `short` values.
| xref:bsl/hash-047.adoc[`hash<signed char>`] 
| Specialization of `hash` for `signed` `char` values.
| xref:bsl/hash-0fb.adoc[`hash<unsigned char>`] 
| Specialization of `hash` for `unsigned` `char` values.
| xref:bsl/hash-08.adoc[`hash<unsigned int>`] 
| Specialization of `hash` for `unsigned` `int` values.
| xref:bsl/hash-0c0.adoc[`hash<unsigned long>`] 
| Specialization of `hash` for `unsigned` `long` values.
| xref:bsl/hash-02.adoc[`hash<unsigned long long>`] 
| Specialization of `hash` for `unsigned` `long long` values.
| xref:bsl/hash-0db.adoc[`hash<unsigned short>`] 
| Specialization of `hash` for `unsigned` `short` values.
| xref:bsl/hash-041.adoc[`hash<wchar_t>`] 
| Specialization of `hash` for `wchar_t` values.
| xref:bsl/hash-0b.adoc[`hash<BSLSTL_KEY const>`] 
| This class provides hashing functionality for constant key types, by delegating to the same function for non‐constant key types.
| xref:bsl/hash-017.adoc[`hash<basic_string<CHAR_TYPE, CHAR_TRAITS, ALLOCATOR>>`] 
| Specialize `bsl::hash` for strings, including an overload for pointers to allow character arrays to be hashed without converting them first.
|===


== Derived Classes

[cols="1,4"]
|===
| Name| Description
| xref:bsl/hash-0b.adoc[`hash<BSLSTL_KEY const>`] 
| This class provides hashing functionality for constant key types, by delegating to the same function for non‐constant key types.
|===


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