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

A concept matching constants that are measured rather than exact by definition

== Synopsis

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

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
template<typename T>
concept MeasuredConstant = Unit<T> && (requires { requires UnitMagnitude<MP_UNITS_NONCONST_TYPE(T::_relative_standard_uncertainty_)>; } ||
              requires { requires Unit<MP_UNITS_NONCONST_TYPE(T::_standard_uncertainty_)>; });
----

== Description

Satisfied by all constants defined with a `relative_standard_uncertainty` or a `standard_uncertainty` argument. Exact constants do not have such an argument, so the distinction is visible to the type system.


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