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<title>Issue 1438: No definition for base()</title>
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<p><em>This page is a snapshot from the LWG issues list, see the <a href="lwg-active.html">Library Active Issues List</a> for more information and the meaning of <a href="lwg-active.html#C++11">C++11</a> status.</em></p>
<h3 id="1438"><a href="lwg-defects.html#1438">1438</a>. No definition for <code>base()</code></h3>
<p><b>Section:</b> 29.5.5.2 <a href="https://wg21.link/rand.adapt.disc">[rand.adapt.disc]</a> <b>Status:</b> <a href="lwg-active.html#C++11">C++11</a>
 <b>Submitter:</b> INCITS <b>Opened:</b> 2010-08-25 <b>Last modified:</b> 2016-01-28</p>
<p><b>Priority: </b>Not Prioritized
</p>
<p><b>View all other</b> <a href="lwg-index.html#rand.adapt.disc">issues</a> in [rand.adapt.disc].</p>
<p><b>View all issues with</b> <a href="lwg-status.html#C++11">C++11</a> status.</p>
<p><b>Discussion:</b></p>
<p><b>Addresses US-126</b></p>

<p>Each adaptor has a member function called <code>base()</code> which has no definition.</p>

<p><i>[
Resolution proposed by ballot comment:
]</i></p>

<blockquote><p>
Give it the obvious definition.
</p></blockquote>

<p><i>[
2010-11-03 Daniel comments and provides a proposed resolution:
]</i></p>


<p>The following proposal adds <code>noexcept</code> specifiers to the declarations of
the <code>base()</code> functions as replacement for a &quot;<i>Throws</i>: Nothing&quot; element.
</p>

<p><i>[
2010 Batavia: The working group reviewed this issue, and recommended to add the following to the Proposed Resolution.
]</i></p>

<ul><li>
Append to paragraph 1 of [rand.req.adapt] (or at the Editor's discretion insert as a new paragraph following that paragraph): 
The expression <code>a.base()</code> shall be valid and shall return a const reference to <code>a</code>'s base engine. 
</li>
</ul>
<p>
After further review, the working group concurred with the Proposed Resolution.
</p>


<p><i>[Batavia: waiting for WEB to review wording]</i></p>




<p id="res-1438"><b>Proposed resolution:</b></p>
<ol>
<li>
Add the following sentence to the end of 29.5.3.5 <a href="https://wg21.link/rand.req.adapt">[rand.req.adapt]</a>/1:
<blockquote><p>
A <i>random number engine adaptor</i> (commonly shortened to <i>adaptor</i>) <code>a</code> of type <code>A</code> is a
random number engine that takes values produced by some other random number engine, and applies an algorithm to
those values in order to deliver a sequence of values with different randomness properties. An engine <code>b</code>
of type <code>B</code> adapted in this way is termed a <i>base engine</i> in this context.<ins> The expression
<code>a.base()</code> shall be valid and shall return a const reference to <code>a</code>'s base engine.</ins>
</p></blockquote>
</li>
<li>Change in [rand.adapt.disc]/3, class template <code>discard_block_engine</code> synopsis, the following declaration:
<blockquote><pre>
// <em>property functions</em>
const Engine&amp; base() const <ins>noexcept</ins>;
</pre></blockquote>
</li>
<li>Add the following new prototype description at the end of sub-clause 29.5.5.2 <a href="https://wg21.link/rand.adapt.disc">[rand.adapt.disc]</a>:
<blockquote>
<pre><ins>const Engine&amp; base() const noexcept;</ins>
</pre>
<blockquote><p>
<ins>? <i>Returns</i>: <code>e</code>.</ins>
</p></blockquote>
</blockquote>
</li>
<li>Change in [rand.adapt.ibits]/4, class template <code>independent_bits_engine</code> synopsis, the following declaration:
<blockquote><pre>
// <em>property functions</em>
const Engine&amp; base() const <ins>noexcept</ins>;
</pre></blockquote>
</li>
<li>Add the following new prototype description at the end of sub-clause 29.5.5.3 <a href="https://wg21.link/rand.adapt.ibits">[rand.adapt.ibits]</a>:
<blockquote>
<pre><ins>const Engine&amp; base() const noexcept;</ins>
</pre>
<blockquote><p>
<ins>? <i>Returns</i>: <code>e</code>.</ins>
</p></blockquote>
</blockquote>
</li>
<li>Change in 29.5.5.4 <a href="https://wg21.link/rand.adapt.shuf">[rand.adapt.shuf]</a>/3, class template <code>shuffle_order_engine</code> synopsis, the following declaration:
<blockquote><pre>
// <em>property functions</em>
const Engine&amp; base() const <ins>noexcept</ins>;
</pre></blockquote>
</li>
<li>Add the following new prototype description at the end of sub-clause 29.5.5.4 <a href="https://wg21.link/rand.adapt.shuf">[rand.adapt.shuf]</a>:
<blockquote>
<pre><ins>const Engine&amp; base() const noexcept;</ins>
</pre>
<blockquote><p>
<ins>? <i>Returns</i>: <code>e</code>.</ins>
</p></blockquote>
</blockquote>
</li>
</ol>





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