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<title>Issue 118: basic_istream uses nonexistent num_get member functions</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#CD1">CD1</a> status.</em></p>
<h3 id="118"><a href="lwg-defects.html#118">118</a>. <code>basic_istream</code> uses nonexistent <code>num_get</code> member functions</h3>
<p><b>Section:</b> 31.7.5.3.2 <a href="https://wg21.link/istream.formatted.arithmetic">[istream.formatted.arithmetic]</a> <b>Status:</b> <a href="lwg-active.html#CD1">CD1</a>
 <b>Submitter:</b> Matt Austern <b>Opened:</b> 1998-11-20 <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#istream.formatted.arithmetic">issues</a> in [istream.formatted.arithmetic].</p>
<p><b>View all issues with</b> <a href="lwg-status.html#CD1">CD1</a> status.</p>
<p><b>Discussion:</b></p>
<p>Formatted input is defined for the types <code>short</code>, <code>unsigned short</code>, <code>int</code>,
<code>unsigned int</code>, <code>long</code>, <code>unsigned long</code>, <code>float</code>, <code>double</code>,
<code>long double</code>, <code>bool</code>, and <code>void*</code>. According to section 27.6.1.2.2,
formatted input of a value <code>x</code> is done as if by the following code fragment: </p>

<pre>typedef num_get&lt; charT,istreambuf_iterator&lt;charT,traits&gt; &gt; numget; 
iostate err = 0; 
use_facet&lt; numget &gt;(loc).get(*this, 0, *this, err, val); 
setstate(err);</pre>

<p>According to section 28.3.4.3.2.2 <a href="https://wg21.link/facet.num.get.members">[facet.num.get.members]</a>, however,
<code>num_get&lt;&gt;::get()</code> is only overloaded for the types
<code>bool</code>, <code>long</code>, <code>unsigned short</code>, <code>unsigned
int</code>, <code>unsigned long</code>, <code>unsigned long</code>,
<code>float</code>, <code>double</code>, <code>long double</code>, and
<code>void*</code>. Comparing the lists from the two sections, we find
that 27.6.1.2.2 is using a nonexistent function for types
<code>short</code> and <code>int</code>. </p>


<p id="res-118"><b>Proposed resolution:</b></p>
<p>In 31.7.5.3.2 <a href="https://wg21.link/istream.formatted.arithmetic">[istream.formatted.arithmetic]</a> Arithmetic Extractors, remove the
two lines (1st and 3rd) which read:</p>
<blockquote>
  <pre>operator&gt;&gt;(short&amp; val);
...
operator&gt;&gt;(int&amp; val);</pre>
</blockquote>

<p>And add the following at the end of that section (27.6.1.2.2) :</p>

<blockquote>
  <pre>operator&gt;&gt;(short&amp; val);</pre>
  <p>The conversion occurs as if performed by the following code fragment (using
  the same notation as for the preceding code fragment):</p>
  <pre>  typedef num_get&lt; charT,istreambuf_iterator&lt;charT,traits&gt; &gt; numget;
  iostate err = 0;
  long lval;
  use_facet&lt; numget &gt;(loc).get(*this, 0, *this, err, lval);
        if (err == 0
                &amp;&amp; (lval &lt; numeric_limits&lt;short&gt;::min() || numeric_limits&lt;short&gt;::max() &lt; lval))
                err = ios_base::failbit;
  setstate(err);</pre>
  <pre>operator&gt;&gt;(int&amp; val);</pre>
  <p>The conversion occurs as if performed by the following code fragment (using
  the same notation as for the preceding code fragment):</p>
  <pre>  typedef num_get&lt; charT,istreambuf_iterator&lt;charT,traits&gt; &gt; numget;
  iostate err = 0;
  long lval;
  use_facet&lt; numget &gt;(loc).get(*this, 0, *this, err, lval);
        if (err == 0
                &amp;&amp; (lval &lt; numeric_limits&lt;int&gt;::min() || numeric_limits&lt;int&gt;::max() &lt; lval))
                err = ios_base::failbit;
  setstate(err);</pre>
</blockquote>

<p><i>[Post-Tokyo: PJP provided the above wording.]</i></p>






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