Error Handling

When an error occurs during execution, the system first searches for a corresponding error handler defined by the user. If no such handler is found, it reports an error message which includes the type of error and the call that raised the error, and aborts execution. For example, when executing the query a=:=1, the system will report:

		  ** Error ** number_expected: a=:=1

where number_expected is the type and a=:=1 is the call.