# Iterator that filters elements by a predicate
        #
        # ~~~~nitish
        # fun lt10(x: Int): Bool do return x < 10
        #
        # var pred = &lt10
        # var xs = [1..20]
        # var actual = xs.iterator.filter(pred).to_a
        # assert actual == [1..9].to_a
        # ~~~~
        fun filter(pred: Fun1[E,Bool]): FilterIter[E]
        do
                return new FilterIter[E](self,pred)
        end