[#std-hash-05b-operator_call]
= xref:std.adoc[std]::xref:std/hash-05b.adoc[hash&lt;folly::enable&lowbar;std&lowbar;hash&lowbar;helper&lt;folly::Optional&lt;T&gt;, remove&lowbar;const&lowbar;t&lt;T&gt;&gt;&gt;]::operator()
:relfileprefix: ../../
:mrdocs:

Computes the hash of an Optional&period;

== Synopsis

Declared in `&lt;folly&sol;Optional&period;h&gt;`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
size&lowbar;t
operator()(xref:folly/Optional.adoc[folly::Optional&lt;T&gt;] const& obj) const;
----

== Return Value

The hash of the contained value, or 0 if empty&period;

== Parameters

[cols="1,4"]
|===
| Name| Description
| *obj*
| The Optional to hash&period;
|===


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