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How to filter events with your module

You may wish to filter events; that is, to interrupt the analysis path depending on whether an event passes your cuts. To do this, call DASH_PASS_EVT or DASH_FAIL_EVT somewhere in your event entrypoint. After your module returns control to DASH, the value of a flag will be tested. If you ``failed'' the event, execution of the analysis path will cease and a new event will be read in. If you ``passed'' the event, the next module in the analysis path will be called.

The above action is controlled by the FILTER command. If you give the command FILTER ON MYANA, then the filtering will happen. You can disable it with FILTER OFF MYANA. Filtering is assumed to be off for module MYANA by default, unless DASH_DEC_FLT('MYANA') is called in DASH_DECL.

You may invert the behavior of your filtering from the command line by specifying FILTER FAILED MYANA. This turns filtering on, but events that ``pass'' the filter criteria are not processed further, whereas events that ``fail'' the filter continue on for further analysis and/or writing to disk.