units
A unit library was needed to be able to represent units of a wide range of disciplines and be able to separate them from the numerical values for use in calculations. The main driver is converting units to a standardized unit set when dealing with user input and output. And be able to use the unit as a singular type that could contain any unit, and not introduce a huge number of types to represent all possible units. Because sometimes the unit type needs to be used inside virtual function calls which must strictly define a type. The libary also has its origin in power systems so support for per-unit operations was also lacking in the alternatives.
Mcneish, CoreyR.↗