t currently stands, because
      the constructor would require taking a reference to a reference, which is currently
      illegal <a class="link" href="background.html#background.references">[7]</a>. Let us consider what
      the constructor's parameters would have to be in order to allow "pair"
      to hold non-reference types, references, and constant references:
    </p>
<div class="table">
<a name="boost_typetraits.background.required_constructor_argument_types"></a><p class="title"><b>Table&#160;1.