t becomes zero.<br />
 <b>Throws:</b> nothing.

<hr />
<pre>
void <a id="pop_back">pop_back</a>();
</pre>

<b>Precondition:</b> <tt>!this-&gt;empty()</tt>.<br />
<b>Effects:</b> Decreases the size of the bitset by one.<br />
 <b>Throws:</b> nothing.

<hr />
<pre>
void <a id="push_back">push_back</a>(bool value);
</pre>

<b>Effects:</b> Increases the size of the bitset by one, and sets
the value of the new most-significant bit to <tt>value</tt>.<br />
 <b>Throws:</b> An allocation error if memory is exhauste