The EVERY-DISTINCT operator treats patterns that return the same value for the specified expression as duplicates and excludes them from pattern evaluation.
Syntax:
every-distinct ( distinctExpression [,distinctExpression] [, ...] [, period] ) subexpression
Patterns having the same value for the distinctExpression are excluded as duplicates after being detected once. If a time sets a period, information held internally for duplicate exclusion purposes is discarded after the specified time has elapsed, and the pattern is once again targeted for evaluation.
