eventfilter takes a single argument which must be a quoted string. It is true if the argument string is a substring of the Event field of the game.
event "Open"An event filter may also be included as a CQL parameter, in addition to be used as an ordinary filter. For example,
cql (input i.pgn event "Open") countsquares 4 10 q
not event "@"
The earliest correct (tested by the
not event "@" above, using the conventions of the Heijden database) 1st prize study is from 1881.
event filter is used in the sample file gameinfo.cql .