Scalar is designed to represent physical scalars and to eliminate errors involving implicit physical units (e.g., confusing angular degrees and radians). The standard arithmetic operators are overloaded to provide syntax identical to that for built-in numeric types. The scalar class does not define any units itself but is part of a package that includes a complete implementation of the standard metric system of units and many standard non-metric units. It also allows the user to define a specialized or reduced set of appropriate physical units for any particular application or domain. Once an application has been developed and tested, the scalar class can easily be switched off, if desired, to achieve the execution efficiency of operations on built-in numeric types, which can be nearly
two orders of magnitude faster. The scalar class can also be used for discrete units to enforce type checking of integer counts, thereby enhancing the built-in dynamic type checking of Python.