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

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

== Synopsis

Declared in `&lt;mp&hyphen;units&sol;framework&sol;unit&lowbar;concepts&period;h&gt;`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
template&lt;typename T&gt;
concept MeasuredConstant = Unit&lt;T&gt; &amp;&amp; (requires &lcub; requires UnitMagnitude&lt;MP&lowbar;UNITS&lowbar;NONCONST&lowbar;TYPE(T&colon;&colon;&lowbar;relative&lowbar;standard&lowbar;uncertainty&lowbar;)&gt;&semi; &rcub; &verbar;&verbar;
              requires &lcub; requires Unit&lt;MP&lowbar;UNITS&lowbar;NONCONST&lowbar;TYPE(T&colon;&colon;&lowbar;standard&lowbar;uncertainty&lowbar;)&gt;&semi; &rcub;);
----

== Description

Satisfied by all constants defined with a `relative&lowbar;standard&lowbar;uncertainty` or a `standard&lowbar;uncertainty` argument&period; Exact constants do not have such an argument, so the distinction is visible to the type system&period;


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