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Merged
jwakely merged 1 commit into from
Nov 6, 2025
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Update PR for 4383. #518

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120 changes: 119 additions & 1 deletion xml/issue4383.xml
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Original file line number Diff line number Diff line change
Expand Up @@ -142,11 +142,129 @@ struct <i>cw-operators</i> {
</ol>
</superseded>

<note>2025-11-04; Zach provides improved wording</note>
<note>2025-11-05; Zach provides improved wording</note>

</discussion>

<resolution>
<p>
This wording is relative to <paper num="N5014"/>.
</p>

<ol>

<li><p>Modify <sref ref="[const.wrap.class]"/>, class template <tt>constant_wrapper</tt> synopsis, as indicated:</p>

<blockquote class="note">
<p>
[<i>Drafting note:</i> The requires clause follows the form of `constant_wrapper`'s
function call operator.]
</p>
</blockquote>

<blockquote>
<pre>
struct <i>cw-operators</i> { // <i>exposition only</i>
[&hellip;]
// <i>pseudo-mutators</i>
<del>template&lt;<i>constexpr-param</i> T&gt;
constexpr auto operator++(this T) noexcept requires requires(T::value_type x) { ++x; }
{ return constant_wrapper&lt;[] { auto c = T::value; return ++c; }()&gt;{}; }
template&lt;<i>constexpr-param</i> T&gt;
constexpr auto operator++(this T, int) noexcept requires requires(T::value_type x) { x++; }
{ return constant_wrapper&lt;[] { auto c = T::value; return c++; }()&gt;{}; }

template&lt;<i>constexpr-param</i> T&gt;
constexpr auto operator--(this T) noexcept requires requires(T::value_type x) { --x; }
{ return constant_wrapper&lt;[] { auto c = T::value; return --c; }()&gt;{}; }
template&lt;<i>constexpr-param</i> T&gt;
constexpr auto operator--(this T, int) noexcept requires requires(T::value_type x) { x--; }
{ return constant_wrapper&lt;[] { auto c = T::value; return c--; }()&gt;{}; }

template&lt;<i>constexpr-param</i> T, <i>constexpr-param</i> R&gt;
constexpr auto operator+=(this T, R) noexcept requires requires(T::value_type x) { x += R::value; }
{ return constant_wrapper&lt;[] { auto v = T::value; return v += R::value; }()&gt;{}; }
template&lt;<i>constexpr-param</i> T, <i>constexpr-param</i> R&gt;
constexpr auto operator-=(this T, R) noexcept requires requires(T::value_type x) { x -= R::value; }
{ return constant_wrapper&lt;[] { auto v = T::value; return v -= R::value; }()&gt;{}; }
template&lt;<i>constexpr-param</i> T, <i>constexpr-param</i> R&gt;
constexpr auto operator*=(this T, R) noexcept requires requires(T::value_type x) { x *= R::value; }
{ return constant_wrapper&lt;[] { auto v = T::value; return v *= R::value; }()&gt;{}; }
template&lt;<i>constexpr-param</i> T, <i>constexpr-param</i> R&gt;
constexpr auto operator/=(this T, R) noexcept requires requires(T::value_type x) { x /= R::value; }
{ return constant_wrapper&lt;[] { auto v = T::value; return v /= R::value; }()&gt;{}; }
template&lt;<i>constexpr-param</i> T, <i>constexpr-param</i> R&gt;
constexpr auto operator%=(this T, R) noexcept requires requires(T::value_type x) { x %= R::value; }
{ return constant_wrapper&lt;[] { auto v = T::value; return v %= R::value; }()&gt;{}; }
template&lt;<i>constexpr-param</i> T, <i>constexpr-param</i> R&gt;
constexpr auto operator&amp;=(this T, R) noexcept requires requires(T::value_type x) { x &amp;= R::value; }
{ return constant_wrapper&lt;[] { auto v = T::value; return v &amp;= R::value; }()&gt;{}; }
template&lt;<i>constexpr-param</i> T, <i>constexpr-param</i> R&gt;
constexpr auto operator|=(this T, R) noexcept requires requires(T::value_type x) { x |= R::value; }
{ return constant_wrapper&lt;[] { auto v = T::value; return v |= R::value; }()&gt;{}; }
template&lt;<i>constexpr-param</i> T, <i>constexpr-param</i> R&gt;
constexpr auto operator^=(this T, R) noexcept requires requires(T::value_type x) { x ^= R::value; }
{ return constant_wrapper&lt;[] { auto v = T::value; return v ^= R::value; }()&gt;{}; }
template&lt;<i>constexpr-param</i> T, <i>constexpr-param</i> R&gt;
constexpr auto operator&lt;&lt;=(this T, R) noexcept requires requires(T::value_type x) { x &lt;&lt;= R::value; }
{ return constant_wrapper&lt;[] { auto v = T::value; return v &lt;&lt;= R::value; }()&gt;{}; }
template&lt;<i>constexpr-param</i> T, <i>constexpr-param</i> R&gt;
constexpr auto operator&gt;&gt;=(this T, R) noexcept requires requires(T::value_type x) { x &gt;&gt;= R::value; }
{ return constant_wrapper&lt;[] { auto v = T::value; return v &gt;&gt;= R::value; }()&gt;{}; }</del>
<ins>template&lt;<i>constexpr-param</i> T&gt;
constexpr auto operator++(this T) noexcept -&gt; constant_wrapper&lt;++Y&gt; { return {}; }
template&lt;<i>constexpr-param</i> T&gt;
constexpr auto operator++(this T, int) noexcept -&gt; constant_wrapper&lt;Y++&gt; { return {}; }
template&lt;<i>constexpr-param</i> T&gt;
constexpr auto operator--(this T) noexcept -&gt; constant_wrapper&lt;--Y&gt; { return {}; }
template&lt;<i>constexpr-param</i> T&gt;
constexpr auto operator--(this T, int) noexcept -&gt; constant_wrapper&lt;Y--&gt; { return {}; }

template&lt;<i>constexpr-param</i> T, <i>constexpr-param</i> R&gt;
constexpr auto operator+=(T, R) noexcept -&gt; constant_wrapper&lt;(T::value += R::value)&gt; { return {}; }
template&lt;<i>constexpr-param</i> T, <i>constexpr-param</i> R&gt;
constexpr auto operator-=(T, R) noexcept -&gt; constant_wrapper&lt;(T::value -= R::value)&gt; { return {}; }
template&lt;<i>constexpr-param</i> T, <i>constexpr-param</i> R&gt;
constexpr auto operator*=(T, R) noexcept -&gt; constant_wrapper&lt;(T::value *= R::value)&gt; { return {}; }
template&lt;<i>constexpr-param</i> T, <i>constexpr-param</i> R&gt;
constexpr auto operator/=(T, R) noexcept -&gt; constant_wrapper&lt;(T::value /= R::value)&gt; { return {}; }
template&lt;<i>constexpr-param</i> T, <i>constexpr-param</i> R&gt;
constexpr auto operator%=(T, R) noexcept -&gt; constant_wrapper&lt;(T::value %= R::value)&gt; { return {}; }
template&lt;<i>constexpr-param</i> T, <i>constexpr-param</i> R&gt;
constexpr auto operator&amp;=(T, R) noexcept -&gt; constant_wrapper&lt;(T::value &amp;= R::value)&gt; { return {}; }
template&lt;<i>constexpr-param</i> T, <i>constexpr-param</i> R&gt;
constexpr auto operator|=(T, R) noexcept -&gt; constant_wrapper&lt;(T::value |= R::value)&gt; { return {}; }
template&lt;<i>constexpr-param</i> T, <i>constexpr-param</i> R&gt;
constexpr auto operator^=(T, R) noexcept -&gt; constant_wrapper&lt;(T::value ^= R::value)&gt; { return {}; }
template&lt;<i>constexpr-param</i> T, <i>constexpr-param</i> R&gt;
constexpr auto operator&lt;&lt;=(T, R) noexcept -&gt; constant_wrapper&lt;(T::value &lt;&lt;= R::value)&gt; { return {}; }
template&lt;<i>constexpr-param</i> T, <i>constexpr-param</i> R&gt;
constexpr auto operator&gt;&gt;=(T, R) noexcept -&gt; constant_wrapper&lt;(T::value &gt;&gt;= R::value)&gt; { return {}; }</ins>
};
}

template&lt;exposition_only::cw_fixed_value X, typename&gt;
struct constant_wrapper: exposition_only::cw_operators {
static constexpr const auto &amp; value = X.data;
using type = constant_wrapper;
using value_type = typename decltype(X)::type;

<del>template&lt;<i>constexpr-param</i> R&gt;
constexpr auto operator=(R) const noexcept requires requires(value_type x) { x = R::value; }
{ return constant_wrapper&lt;[] { auto v = value; return v = R::value; }()&gt;{}; }</del>
<ins>template&lt;<i>constexpr-param</i> R&gt;
constexpr auto operator=(R) const noexcept -&gt; constant_wrapper&lt;X = R::value&gt; { return {}; }</ins>

constexpr operator decltype(auto)() const noexcept { return value; }
};

</pre>
</blockquote>

</li>

</ol>

</resolution>

</issue>