context function 2: not-filter

        not-filter(operators, conditions) input-seq
        Filters the input sequence to only those elements that don't satisfy the operator/condition pair
        It is the brother of filter()

        -- First, learn some knowledge:
        father |John> => |Fred>
        occupation |Fred> => |politician>

        father |Sam> => |Robert>
        occupation |Robert> => |doctor>

        father |Emma> => |Jack>
        occupation |Jack> => |nurse>

        -- filter to those that don't have a rule of any type that is doctor or nurse:
        -- NB: if rel-kets[*] is large, or supported-ops is large, this may be slow.
        not-filter(|*>, |doctor> + |nurse>) rel-kets[*]
            |John> + |Fred> + |Sam> + |Emma>

        -- find people that don't have the father operator defined:
        not-filter(|op: father>, |*>) rel-kets[*]
            |Fred> + |Robert> + |Jack>

        -- filter to people that don't have a father with occupation of either doctor or nurse:
        not-filter(|ops: occupation father>, |doctor> + |nurse>) rel-kets[*]
            |John> + |Fred> + |Robert> + |Jack>

    see also: