There are several predefined operators in VHDL that perform various
calculations on their operands. Because VHDL has strong data typing
rules, most of the operators require both operands to be of the same
type. A notable exception to this rule, however, is that physical
types may be multiplied and divided by integers and real numbers with
the result being a physical type. Similarly, although most operators
generate results of the same type as one or both of their operands,
the result of an expression with an relational operator is a Boolean
value.
