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    CWG Issue 1515</TITLE>
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<P><EM>This is an unofficial snapshot of the ISO/IEC JTC1 SC22 WG21
  Core Issues List revision 118b.
  See http://www.open-std.org/jtc1/sc22/wg21/ for the official
  list.</EM></P>
<P>2025-09-28</P>
<HR>
<A NAME="1515"></A><H4>1515.
  
Modulo 2<SUP><I>n</I></SUP> arithmetic for implicitly-unsigned types
</H4>
<B>Section: </B>6.9.2&#160; [<A href="https://wg21.link/basic.fundamental">basic.fundamental</A>]
 &#160;&#160;&#160;

 <B>Status: </B>CD3
 &#160;&#160;&#160;

 <B>Submitter: </B>Sean Hunt
 &#160;&#160;&#160;

 <B>Date: </B>2012-07-03<BR>


<P>[Moved to DR at the April, 2013 meeting.]</P>

<P>According to 6.9.2 [<A href="https://wg21.link/basic.fundamental#4">basic.fundamental</A>] paragraph 4,</P>

<BLOCKQUOTE>

Unsigned integers, declared <TT>unsigned</TT>, shall obey the laws of
arithmetic modulo 2<SUP><I>n</I></SUP> where <I>n</I> is the number of
bits in the value representation of that particular size of integer.

</BLOCKQUOTE>

<P>It is not clear whether this wording intentionally excludes types
like <TT>char16_t</TT> and <TT>char32_t</TT> (and, possibly, types
<TT>char</TT> and <TT>wchar_t</TT>, if those types are unsigned in
a given implementation), since the <TT>unsigned</TT> keyword is not
used in their declaration.</P>

<P><B>Proposed resolution (October, 2012):</B></P>

<P>Change 6.9.2 [<A href="https://wg21.link/basic.fundamental#4">basic.fundamental</A>] paragraph 4 as follows:</P>

<BLOCKQUOTE>

Unsigned integers<DEL>, declared <TT>unsigned</TT>,</DEL> shall obey
the laws of arithmetic modulo 2<SUP><I>n</I></SUP> where <I>n</I> is
the number of bits in the value representation of that particular size
of integer.<SUP>46</SUP>

</BLOCKQUOTE>

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