How does a filter term in a function argument work?
In ‘filter’ and ‘member’ list functions a term is supplied as one of the arguments which is effectively a ‘comparison’ expression. The ‘comparison’ function must return a logical(Boolean – TRUE/FALSE) data type. Such functions always have another argument which accepts a list of rows. The row type of this list is the context row type for the ‘comparison’ expression. The ‘comparison’ expression is evaluated in the context of each row in the target list one at a time. The function then uses these results in a way appropriate to its purpose.
