[#mp_units-named_unit-0ec]
= xref:mp_units.adoc[mp_units]::named_unit
:relfileprefix: ../
:mrdocs:

A named unit

== Synopsis

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

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
template<
    xref:mp_units/symbol_text-032.adoc[symbol_text] Symbol,
    auto...>
struct named_unit;
----

== Description

Defines a unit with a special name. It may be used to provide a base unit in the system of units (e.g. `metre`) or a name assigned to another scaled or derived unit (e.g. `hour`, `joule`). Most of the named units may be composed with a prefix to create a `prefixed_unit`.

For example:

[,cpp]
----
{.cpp}
 inline constexpr struct second final : named_unit<"s", kind_of<time>> {} second;
 inline constexpr struct metre final : named_unit<"m", kind_of<length> {} metre;
 inline constexpr struct hertz final : named_unit<"Hz", inverse(second), kind_of<frequency>> {} hertz;
 inline constexpr struct newton final : named_unit<"N", kilogram * metre / square(second)> {} newton;
 inline constexpr struct degree_Celsius final : named_unit<{u8"℃", "`C"}, kelvin, zeroth_degree_Celsius> {}
 degree_Celsius; inline constexpr struct minute final : named_unit<"min", mag<60> * second> {} minute;
----
[NOTE]
====
A common convention in this library is to assign the same name for a type and an object of this type&period; Besides defining them user never works with the unit types in the source code&period; All operations are done on the objects&period; Contrarily, the unit types are the only one visible in the compilation errors&period; Having them of the same names improves user experience and somehow blurs those separate domains&period;

====

== Derived Classes

[cols="1,4"]
|===
|Name|Description

| xref:mp_units/parts_per_million-0f.adoc[`parts&lowbar;per&lowbar;million`]
| 
| xref:mp_units/per_mille-01.adoc[`per&lowbar;mille`]
| 
| xref:mp_units/percent-02.adoc[`percent`]
| 
|===

== Template Parameters

[cols="1,4"]
|===
|Name|Description

| *Symbol*
| a short text representation of the unit
|===


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