Range Iterator for Salesforce. It is probably most useful in a batch class.

RangeIterator.cls

public class RangeIterator implements Iterable<Integer> {
    Integer start;
    Integer stop;

    public RangeIterator(Integer start, Integer stop) {
        this.start = start;
        this.stop = stop;
    }
    public Iterator<Integer> iterator() {
        return new RangeIterable(start, stop);
    }

    public class RangeIterable implements Iterator<Integer> {
        Integer start;
        Integer stop;
        Integer current;

        public RangeIterable(Integer start, Integer stop) {
            this.start = start;
            this.stop = stop;
            if (start == null || stop == null || start > stop) {
                throw new GeneralException('invalid arguments');
            }
            this.current = this.start;
        }

        public Boolean hasNext() {
            return current <= stop;
        }

        public Integer next() {
            return current++;
        }
    }
}

RangeIteratorTest.cls

@IsTest
public class RangeIteratorTest {
    @IsTest
    static void it_should_iterate_over_range() {
        RangeIterator iterator = new RangeIterator(0, 10);
        Iterator<Integer> iterable = iterator.iterator();
        System.assertEquals(true, iterable.hasNext());
        System.assertEquals(0, iterable.next());
        System.assertEquals(true, iterable.hasNext());
        System.assertEquals(1, iterable.next());
        System.assertEquals(true, iterable.hasNext());
        System.assertEquals(2, iterable.next());
        System.assertEquals(true, iterable.hasNext());
        System.assertEquals(3, iterable.next());
        System.assertEquals(true, iterable.hasNext());
        System.assertEquals(4, iterable.next());
        System.assertEquals(true, iterable.hasNext());
        System.assertEquals(5, iterable.next());
        System.assertEquals(true, iterable.hasNext());
        System.assertEquals(6, iterable.next());
        System.assertEquals(true, iterable.hasNext());
        System.assertEquals(7, iterable.next());
        System.assertEquals(true, iterable.hasNext());
        System.assertEquals(8, iterable.next());
        System.assertEquals(true, iterable.hasNext());
        System.assertEquals(9, iterable.next());
        System.assertEquals(true, iterable.hasNext());
        System.assertEquals(10, iterable.next());
        System.assertEquals(false, iterable.hasNext());
    }
}