Units users,<br><br>I&#39;m sure this is an include I am missing somewhere. I&#39;ve got a derived physical dimension defined as derived_dimension&lt;volume_dimension,1&gt;, and the corresponding unit&lt;my_dimension,si::system&gt;, however the to_string() of the quantity shows &quot;dimensionless&quot;. I am expecting this should be &quot;m^3&quot;?<br>
<br>Regards,<br><br>Michael<br>