s of
<tt>struct</tt>/<tt>union</tt> types. All other accesses defer
to the corresponding metamethods or index tables (if any).
</p>
<p>
Note: since there's (deliberately) no address-of operator, a cdata
object holding a value type is effectively immutable after
initialization. The JIT compiler benefits from this fact when applying
certain optimizations.
</p>
<p>
As a consequence, the <em>elements</em> of complex numbers and
vectors are immutable. But the elements of an aggregate holding these
types <em>may<