n></code>.
        The algorithm tests the elements of a sequence and returns true if exactly
        one of the elements in the sequence has a particular property.
      </p>
<p>
        The routine <code class="computeroutput"><span class="identifier">one_of</span></code> takes
        a sequence and a predicate. It will return true if the predicate returns
        true for one element in the sequence.
      </p>
<p>
        The routine <code class="computeroutput"><span class="identifier">one_of_equal</s