[#mp_units-quantity_character]
= xref:mp_units.adoc[mp&lowbar;units]::quantity&lowbar;character
:relfileprefix: ../
:mrdocs:

Quantity character

== Synopsis

Declared in `&lt;mp&hyphen;units&sol;framework&sol;quantity&lowbar;character&period;h&gt;`

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

== Description

A quantity character classifies a quantity along two orthogonal axes&colon;

* its _tensor order_ (`quantity&lowbar;tensor&lowbar;order`)&colon; scalar (order 0), vector (order 1), or tensor (order 2), and
* its _numeric field_ (`quantity&lowbar;field`)&colon; real or complex&period;

Scalars, vectors, and tensors are mathematical objects independent of the choice of a coordinate system, whereas their components depend on it&period; A scalar has magnitude but no direction&semi; a vector possesses both magnitude and direction&semi; a tensor (for example the Cauchy stress tensor) additionally carries orientation&period; The numeric field separately distinguishes real quantities from complex ones (such as a voltage phasor or a complex permittivity), which affects the operations a quantity admits&period;

The pre&hyphen;2&period;6&period;0 flat spelling (`quantity&lowbar;character&colon;&colon;real&lowbar;scalar`, `&colon;&colon;complex&lowbar;scalar`, `&colon;&colon;vector`, `&colon;&colon;tensor`) remains available for backward compatibility and maps onto the two axes&period;

== Member Functions

[cols="1,4"]
|===
| Name| Description
| xref:mp_units/quantity_character/2constructor-05.adoc[`quantity&lowbar;character`]         [.small]#[constructor]#
| Constructors
|===


== Data Members

[cols="1"]
|===
| Name
| xref:mp_units/quantity_character/field.adoc[`field`] 
| xref:mp_units/quantity_character/order.adoc[`order`] 
|===


== Friends

[cols="1,4"]
|===
| Name| Description
| `mp&lowbar;units::operator&equals;&equals;`
| 
| `xref:mp_units/operator_3way-01.adoc[mp&lowbar;units::operator&lt;&equals;&gt;]`
| Three&hyphen;way comparison operator
|===


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