[#bsl-unordered_set-0b4]
= xref:bsl.adoc[bsl]::xref:bsl/unordered_set-0d2d.adoc[unordered_set<KEY, HASH, EQUAL, ALLOCATOR>]
:relfileprefix: ../
:mrdocs:

Deduce the template parameter `KEY` from the `value_type` of the initializer_list supplied to the constructor of `unordered_set`. Deduce the template parameters `HASH`, EQUAL and `ALLOCATOR` from the other parameters passed to the constructor. This deduction guide does not participate unless: (1) the supplied `HASH` is invocable with a `KEY`, (2) the supplied `EQUAL` is invocable with two `KEY`s, and (3) the supplied allocator meets the requirements of a standard allocator.

== Synopsis

Declared in `<bslstl_unorderedset.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
template<
    class KEY,
    class HASH = xref:bsl/hash-06.adoc[bsl::hash<KEY>],
    class EQUAL = xref:bsl/equal_to-0d.adoc[bsl::equal_to<KEY>],
    class ALLOCATOR = xref:bsl/allocator-0df.adoc[bsl::allocator<KEY>]>
requires std::is_invocable_v<HASH, const KEY&> && std::is_invocable_v<EQUAL, const KEY&, const KEY&> && bsl::IsStdAllocator_v<ALLOCATOR>
xref:bsl/unordered_set-0d2d.adoc[unordered_set<KEY, HASH, EQUAL, ALLOCATOR>](
    std::initializer_list<KEY>,
    bsl::allocator_traits<ALLOCATOR>::size_type,
    HASH,
    EQUAL,
    ALLOCATOR) -> xref:bsl/unordered_set-0d2d.adoc[unordered_set<KEY, HASH, EQUAL, ALLOCATOR>];
----


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