operand of any operator must be a valid actor for
        lazy evaluation to take effect. To force lazy evaluation of an ordinary expression,
        we can use <code class="computeroutput"><span class="identifier">ref</span><span class="special">(</span><span class="identifier">x</span><span class="special">)</span></code>, <code class="computeroutput"><span class="identifier">val</span><span class="special">(</span><span class="identifier">x</span><span class="special">)</span></code> or <code class="comp