[#mp_units-utility-unspecified_t]
= xref:mp_units.adoc[mp&lowbar;units]::xref:mp_units/utility.adoc[utility]::unspecified&lowbar;t
:relfileprefix: ../../
:mrdocs:

Sentinel default for a specializable variable&hyphen;template customization point with no usable default&period;

== Synopsis

Declared in `&lt;mp&hyphen;units&sol;utility&sol;unspecified&period;h&gt;`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
struct unspecified&lowbar;t;
----

== Description

A variable template cannot be `&equals; delete`d the way a function can, so a customization point that must be specialized before use defaults to `unspecified`, and a specialization replaces it with a real value&period; `specified` reports whether that has happened&period; This is public authoring vocabulary shared by the library&apos;s own customization points and by higher&hyphen;level tools, hence it lives in the `mp&lowbar;units&colon;&colon;utility` namespace&period;


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