[#mp_units-vector_components]
= xref:mp_units.adoc[mp_units]::vector_components
:relfileprefix: ../
:mrdocs:

Opts a vector quantity into decomposition into named 1D‐vector components

== Synopsis

Declared in `<mp‐units/framework/customization_points.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
template<xref:mp_units/QuantitySpec.adoc[QuantitySpec] auto QS>
requires (get_character(QS).order == quantity_tensor_order::vector) &&
          (!detail::QuantityKindSpec<MP_UNITS_REMOVE_CONST(decltype(QS))>)
struct vector_components;
----

== Description

Specialize for a vector `quantity_spec` and inherit from `vector_axes,` listing the per‐axis quantity specs in coordinate order (see `mp‐units/framework/vector_components.h)`

[,cpp]
----
template<>
struct mp_units::vector_components<flight_velocity> :
    mp_units::vector_axes<forward_velocity, wind_drift, sink_rate> {};
----
Left undefined (the quantity is not decomposable) unless specialized&period; Only a concrete vector quantity spec may be decomposed, so a specialization for a non&hyphen;vector spec or for a `kind&lowbar;of&lt;&gt;` quantity kind is ill&hyphen;formed&period;

== Template Parameters

[cols="1,4"]
|===
| Name| Description
| *QS*
| the vector quantity spec being decomposed
|===


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