Functions Functions Function-style primitives are different from operators only in the syntax used to include them in formulas. Argument values do not have to be simple numbers, they can be formulas of any complexity.
Some primitives use optional arguments.
These arguments have default values that are used if you don't supply your own argument values. By convention, arguments presented in bold are required and all others are optional. All remaining arguments have default values. When a primitive accepts optional arguments, all arguments after the first optional one are always optional as well. This allows you to simply truncate the argument list.