Subclause [qty.sym.expr] specifies the components
used to maintain ordered, simplified, and readable
argument lists in the names of specializations.
[Example 1: usingnamespace si::unit_symbols;
int x = kg * km / square(h); // error: cannot construct from// derived_unit<si::kilo_<si::gram>, si::kilo_<si::metre>, per<power<non_si::hour, 2>>>
The library ensures decltype(kg * km / square(h)) is styled-like as commented in diagnostics,
provided that, in the implementation-defined total order of types,
decltype(kg) is less than decltype(km).