ult constructor.  No memory is allocated; the length of the vector is
zero. The
vector may subsequently be resized using resize(), or used to refer to another
vector's data using reference().<br></li>

<br><li>
<b>Vector(size_t length)</b><br><br>
Create a new vector of the given length.  Memory is allocated using
<b>new</b>.  Elements are not initialized.<br></li>

<br><li>
<b>Vector(Vector&lt;T_numtype&gt;& x)</b><br><br>
Creates a reference (or alias) to the data of vector x.  Both x and this
vector now 