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<title>Issue 867: Valarray and value-initialization</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#NAD_Editorial">NAD Editorial</a> status.</em></p>
<h3 id="867"><a href="lwg-closed.html#867">867</a>. Valarray and value-initialization</h3>
<p><b>Section:</b> 29.6.2.2 <a href="https://wg21.link/valarray.cons">[valarray.cons]</a> <b>Status:</b> <a href="lwg-active.html#NAD_Editorial">NAD Editorial</a>
 <b>Submitter:</b> Alberto Ganesh Barbati <b>Opened:</b> 2008-07-20 <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#valarray.cons">issues</a> in [valarray.cons].</p>
<p><b>View all issues with</b> <a href="lwg-status.html#NAD Editorial">NAD Editorial</a> status.</p>
<p><b>Discussion:</b></p>
<p>
From 29.6.2.2 <a href="https://wg21.link/valarray.cons">[valarray.cons]</a>, paragraph 2:
</p>

<blockquote><pre>
explicit  valarray(size_t);
</pre>
<blockquote><p>
The array created by this constructor has a length equal to the value of the argument. The elements
of the array are constructed using the default constructor for the instantiating type <code>T</code>.
</p></blockquote>
</blockquote>

<p>
The problem is that the most obvious <code>T</code>s for <code>valarray</code> are <code>float</code>
and <code>double</code>, they don't have a default constructor. I guess the intent is to value-initialize
the elements, so I suggest replacing:
</p>

<blockquote><p>
The elements of the array are constructed using the default constructor for the instantiating type <code>T</code>.
</p></blockquote>
<p>
with
</p>
<blockquote><p>
The elements of the array are value-initialized.
</p></blockquote>

<p>
There is another reference to the default constructor of <code>T</code> in the non-normative note in paragraph 9.
That reference should also be replaced. (The normative wording in paragraph 8 refers to <code>T()</code>
and so it doesn't need changes).
</p>

<p><i>[
Batavia (2009-05):
]</i></p>

<blockquote><p>
We agree with the proposed resolution.
Move to NAD Editorial.
</p></blockquote>


<p id="res-867"><b>Proposed resolution:</b></p>
<p>
Change 29.6.2.2 <a href="https://wg21.link/valarray.cons">[valarray.cons]</a>, paragraph 2:
</p>

<blockquote>
<pre>
explicit  valarray(size_t);
</pre>
<blockquote><p>
The array created by this constructor has a length equal to the value of the argument. The elements
of the array are <del>constructed using the default constructor for the instantiating type <code>T</code></del>
<ins>value-initialized (9.5 <a href="https://wg21.link/dcl.init">[dcl.init]</a>)</ins>.
</p></blockquote>
</blockquote>

<p>
Change 29.6.2.8 <a href="https://wg21.link/valarray.members">[valarray.members]</a>, paragraph 9:
</p>

<blockquote><p>
[<i>Example:</i> If the argument has the value -2, the first two elements of the result will be <del>constructed using the 
default constructor</del>
<ins>value-initialized (9.5 <a href="https://wg21.link/dcl.init">[dcl.init]</a>)</ins>;
the third element of the result will be assigned the value of the first element of the argument; etc. <i>-- end example</i>]
</p></blockquote>






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