m (<code class="json">String</code>, <code class="json">Array</code> or <code class="json">Object</code>).  Similarly, an aggregate constructor is invoked at the end of a well-formed aggregate datum, and is supposed to return the Lisp value that corresponds to the whole aggregate.  A member handler is invoked when the parser reads past a member of an <code class="json">Array</code>, or a key or value of an <code class="json">Object</code>; it is passed the value which the constructor for that member datum h