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

Quantity character

== Synopsis

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

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
struct quantity_character;
----

== Description

A quantity character classifies a quantity along two orthogonal axes:

* its _tensor order_ (`quantity_tensor_order`): scalar (order 0), vector (order 1), or tensor (order 2), and
* its _numeric field_ (`quantity_field`): real or complex.

Scalars, vectors, and tensors are mathematical objects independent of the choice of a coordinate system, whereas their components depend on it. A scalar has magnitude but no direction; a vector possesses both magnitude and direction; a tensor (for example the Cauchy stress tensor) additionally carries orientation. 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.

The pre‐2.6.0 flat spelling (`quantity_character::real_scalar`, `::complex_scalar`, `::vector`, `::tensor`) remains available for backward compatibility and maps onto the two axes.

== Member Functions

[cols="1,4"]
|===
| Name| Description
| xref:mp_units/quantity_character/2constructor-05.adoc[`quantity_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_units::operator==`
| 
| `xref:mp_units/operator_3way-01.adoc[mp_units::operator<=>]`
| Three‐way comparison operator
|===


[.small]#Created with https://www.mrdocs.com[MrDocs]#