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<title>Issue 359: num_put&lt;&gt;::do_put (..., bool) undocumented</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="359"><a href="lwg-defects.html#359">359</a>. num_put&lt;&gt;::do_put (..., bool) undocumented</h3>
<p><b>Section:</b> 28.3.4.3.3.2 <a href="https://wg21.link/facet.num.put.members">[facet.num.put.members]</a> <b>Status:</b> <a href="lwg-active.html#CD1">CD1</a>
 <b>Submitter:</b> Martin Sebor <b>Opened:</b> 2002-03-12 <b>Last modified:</b> 2016-01-28</p>
<p><b>Priority: </b>Not Prioritized
</p>
<p><b>View all issues with</b> <a href="lwg-status.html#CD1">CD1</a> status.</p>
<p><b>Discussion:</b></p>
<p>22.2.2.2.1, p1:</p>

    <pre>
    iter_type put (iter_type out, ios_base&amp; str, char_type fill,
                   bool val) const;
    ...

    1   Returns: do_put (out, str, fill, val).
    </pre>

<p>AFAICS, the behavior of do_put (..., bool) is not documented anywhere,
however, 22.2.2.2.2, p23:</p>

<blockquote>
<pre>
iter_type put (iter_type out, ios_base&amp; str, char_type fill,
               bool val) const;
</pre>


        <p>Effects: If (str.flags() &amp; ios_base::boolalpha) == 0 then do
             out = do_put(out, str, fill, (int)val)
           Otherwise do</p>
<pre>
             string_type s =
                 val ? use_facet&lt;ctype&lt;charT&gt; &gt;(loc).truename()
                     : use_facet&lt;ctype&lt;charT&gt; &gt;(loc).falsename();
</pre>
           <p>and then insert the characters of s into out. <i>out</i>.</p>
</blockquote>

<p>
This means that the bool overload of <code>do_put()</code> will never be called,
which contradicts the first paragraph. Perhaps the declaration
should read <code>do_put()</code>, and not <code>put()</code>?
</p>

<p>
Note also that there is no <b>Returns</b> clause for this function, which
should probably be corrected, just as should the second occurrence
of <i>"out."</i> in the text.
</p>

<p>
I think the least invasive change to fix it would be something like
the following:
</p>


<p id="res-359"><b>Proposed resolution:</b></p>
<p>In 28.3.4.3.3.3 <a href="https://wg21.link/facet.num.put.virtuals">[facet.num.put.virtuals]</a>, just above paragraph 1, remove
  the <code>bool</code> overload.</p>

<p>
In 28.3.4.3.3.3 <a href="https://wg21.link/facet.num.put.virtuals">[facet.num.put.virtuals]</a>, p23, make the following changes
</p>

<blockquote><p>
     Replace <code>put()</code> with <code>do_put()</code> in the declaration
     of the member function.
</p></blockquote>

<blockquote><p>
    Change the <b>Effects</b> clause to a <b>Returns</b> clause (to
    avoid the requirement to call <code>do_put(..., int)</code> from <code>
    do_put (..., bool))</code>
    like so:
</p></blockquote>

<blockquote><p>
    23   <b>Returns</b>: If <code>(str.flags() &amp;
         ios_base::boolalpha) == 0</code> then
         <code>do_put (out, str, fill, (long)val)</code>
         Otherwise the function obtains a string <code>s</code> as if by</p>
<pre>
             string_type s =
                val ? use_facet&lt;ctype&lt;charT&gt; &gt;(loc).truename()
                    : use_facet&lt;ctype&lt;charT&gt; &gt;(loc).falsename();
</pre>
         <p>and then inserts each character <code>c</code> of s into out via
           <code>*out++ = c</code>
         and returns <code>out</code>.</p>
</blockquote>



<p><b>Rationale:</b></p><p>
This fixes a couple of obvious typos, and also fixes what appears to
be a requirement of gratuitous inefficiency.
</p>




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