[#BloombergLP-bslstl-HashTable_HashWrapper-03]
= xref:BloombergLP.adoc[BloombergLP]::xref:BloombergLP/bslstl.adoc[bslstl]::HashTable_HashWrapper
:relfileprefix: ../../
:mrdocs:

Wrapper ensuring a hash functor's call operator is const‐qualified.

== Synopsis

Declared in `<bslstl_hashtable.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
template<class FUNCTOR>
class HashTable_HashWrapper;
----

== Description

This class provides a wrapper around a functor satisfying the `Hash` requirements ({`bslstl_hash`}) such that the function call operator is always declared as `const` qualified.

TBD Provide an optimization for the case of an empty base functor, where we can safely const_cast want calling the base class operator.

Note that we would only one class, not two, with C++11 variadic templates and perfect forwarding, and we could also easily detect whether or not `FUNCTOR` provided a const‐qualified `operator()`.

== Member Functions

[cols="1,4"]
|===
| Name| Description
| xref:BloombergLP/bslstl/HashTable_HashWrapper-03/2constructor-00.adoc[`HashTable_HashWrapper`]         [.small]#[constructor]#
| Constructors
| xref:BloombergLP/bslstl/HashTable_HashWrapper-03/functor.adoc[`functor`] 
| Return a reference to the wrapped hash functor.
| xref:BloombergLP/bslstl/HashTable_HashWrapper-03/operator_call.adoc[`operator()`] 
| Call the wrapped hash functor with `arg`.
| xref:BloombergLP/bslstl/HashTable_HashWrapper-03/swap.adoc[`swap`] 
| Exchange the wrapped hash functor with that of `other`.
|===


== Specializations

[cols="1,4"]
|===
| Name| Description
| xref:BloombergLP/bslstl/HashTable_HashWrapper-02.adoc[`HashTable_HashWrapper<FUNCTOR const>`] 
| Partial specialization for const‐qualified hash functors.
| xref:BloombergLP/bslstl/HashTable_HashWrapper-0d.adoc[`HashTable_HashWrapper<FUNCTOR&>`] 
| Partial specialization for const‐qualified hash functors.
|===


== Non-Member Functions

[cols="1,4"]
|===
| Name| Description
| xref:BloombergLP/bslstl/swap-040.adoc[`swap`]
| Swap the functors wrapped by `a` and `b`.
|===


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