inal value.

        <p>If no final value is specified, the variable will be stepped forever. 
Using <code>from</code> or <code>upfrom</code> will result in increasing values,
while <code>downfrom</code> will give decreasing values.

        <p>On each iteration, <var>var</var> is incremented or decremented by the
value of the sequence keyword <code>by</code>, which defaults to 1.  It
should always be a positive number, even for downward iterations.

        <p>In the following examples, the sequence of num