An aggregate UDF is a V3 or V4 external C or C++ procedure that operates on multiple values. Aggregate UDFs are also sometimes known as UDAs or UDAFs. The context structure for coding aggregate UDFs is slightly different than the context structure used for coding scalar UDFs.
See User-Defined Functions for detailed information and examples. External C and C++ procedures require a separately licensed SAP Sybase IQ option.