ass="computeroutput"><span class="identifier">seed</span> <span class="identifier">a</span></code>"
            returns an <code class="computeroutput"><span class="identifier">expression</span></code>
            object that keep tracks of the type of <code class="computeroutput"><span class="identifier">a</span></code>.
            This expression has overloads for left-to-right associativity, and the
            operations <code class="computeroutput"><span class="identifier">op1</span></code>, <code cla