Operator functions
An operator function is a user-defined function, such as plus() or equal(), that has a corresponding operator symbol. For an operator function to operate on the opaque data type, you must overload the routine for the opaque data type.
For general information about the operator functions that the database server provides, see Operators and operator functions. For general information about overloading routines, refer to Routine overloading. For information about how to overload an operator function on an opaque data type, see Arithmetic and text operator functions for opaque data types.