From 2370288a79f29c5c51c3480d03fc7c4597ff88b0 Mon Sep 17 00:00:00 2001
From: jzmaddock <john@johnmaddock.co.uk>
Date: Mon, 21 Nov 2022 18:24:04 +0000
Subject: [PATCH] Update operators docs. Fixes
 https://github.com/boostorg/type_traits/issues/160.

---
 .../category/value_traits/operators.html      | 35 ++++++++++++-------
 doc/html/index/s11.html                       |  2 +-
 doc/html/index/s12.html                       |  2 +-
 doc/html/index/s13.html                       |  2 +-
 doc/html/index/s14.html                       |  2 +-
 doc/operators.qbk                             | 12 ++++---
 6 files changed, 34 insertions(+), 21 deletions(-)

diff --git a/doc/html/boost_typetraits/category/value_traits/operators.html b/doc/html/boost_typetraits/category/value_traits/operators.html
index 588467d..e52ab9b 100644
--- a/doc/html/boost_typetraits/category/value_traits/operators.html
+++ b/doc/html/boost_typetraits/category/value_traits/operators.html
@@ -1148,7 +1148,15 @@
           All traits are implemented the same way using preprocessor macros to avoid
           code duplication. The main files are in <code class="literal">boost/type_traits/detail</code>:
           <code class="literal">has_binary_operator.hpp</code>, <code class="literal">has_prefix_operator.hpp</code>
-          and <code class="literal">has_postfix_operator.hpp</code>. The example of prefix
+          and <code class="literal">has_postfix_operator.hpp</code>.
+        </p>
+<p>
+          Given a sufficiently conforming C++11 compiler, these traits are implemented
+          in a rather compact and straightforward way that should always give accurate
+          answers.
+        </p>
+<p>
+          In C++03 there is a legacy implementation, by way of example the prefix
           <code class="computeroutput"><span class="keyword">operator</span><span class="special">-</span></code>
           is presented below:
         </p>
@@ -1324,7 +1332,7 @@
           <span class="phrase"><a name="boost_typetraits.category.value_traits.operators.limitation"></a></span><a class="link" href="operators.html#boost_typetraits.category.value_traits.operators.limitation">Limitation</a>
         </h6>
 <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">
-              Requires a compiler with working SFINAE.
+              Prior to C++11, requires a compiler with working SFINAE.
             </li></ul></div>
 <h6>
 <a name="boost_typetraits.category.value_traits.operators.h6"></a>
@@ -1333,21 +1341,22 @@
         </h6>
 <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
 <li class="listitem">
-              These traits cannot detect whether the operators are public or not:
-              if an operator is defined as a private member of type <code class="computeroutput"><span class="identifier">T</span></code> then the instantiation of the corresponding
-              trait will produce a compiler error. For this reason these traits cannot
-              be used to determine whether a type has a public operator or not.
+              Prior to C++11, these traits cannot detect whether the operators are
+              public or not: if an operator is defined as a private member of type
+              <code class="computeroutput"><span class="identifier">T</span></code> then the instantiation
+              of the corresponding trait will produce a compiler error. For this
+              reason these traits cannot be used to determine whether a type has
+              a public operator or not.
 <pre class="programlisting"><span class="keyword">struct</span> <span class="identifier">A</span> <span class="special">{</span> <span class="keyword">private</span><span class="special">:</span> <span class="identifier">A</span> <span class="keyword">operator</span><span class="special">-();</span> <span class="special">};</span>
 <span class="identifier">boost</span><span class="special">::</span><span class="identifier">has_unary_minus</span><span class="special">&lt;</span><span class="identifier">A</span><span class="special">&gt;::</span><span class="identifier">value</span><span class="special">;</span> <span class="comment">// error: A::operator-() is private</span>
 </pre>
             </li>
 <li class="listitem">
-              There is an issue if the operator exists only for type <code class="computeroutput"><span class="identifier">A</span></code> and <code class="computeroutput"><span class="identifier">B</span></code>
-              is convertible to <code class="computeroutput"><span class="identifier">A</span></code>.
-              In this case, the compiler will report an ambiguous overload because
-              both the existing operator and the one we provide (with argument of
-              type <code class="computeroutput"><span class="identifier">any</span></code>) need type
-              conversion, so that none is preferred.
+              Prior to C++11, there is an issue if the operator exists only for type
+              <code class="computeroutput"><span class="identifier">A</span></code> and <code class="computeroutput"><span class="identifier">B</span></code> is convertible to <code class="computeroutput"><span class="identifier">A</span></code>. In this case, the compiler will
+              report an ambiguous overload because both the existing operator and
+              the one we provide (with argument of type <code class="computeroutput"><span class="identifier">any</span></code>)
+              need type conversion, so that none is preferred.
 <pre class="programlisting"><span class="keyword">struct</span> <span class="identifier">A</span> <span class="special">{</span> <span class="special">};</span>
 <span class="keyword">void</span> <span class="keyword">operator</span><span class="special">-(</span><span class="keyword">const</span> <span class="identifier">A</span><span class="special">&amp;);</span>
 <span class="keyword">struct</span> <span class="identifier">B</span> <span class="special">{</span> <span class="keyword">operator</span> <span class="identifier">A</span><span class="special">();</span> <span class="special">};</span>
@@ -1388,7 +1397,7 @@
 
 <span class="keyword">class</span> <span class="identifier">bad</span> <span class="special">{</span> <span class="special">};</span>
 <span class="keyword">class</span> <span class="identifier">good</span> <span class="special">{</span> <span class="special">};</span>
-<span class="keyword">bool</span> <span class="identifier">f</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">good</span><span class="special">&amp;,</span> <span class="keyword">const</span> <span class="identifier">good</span><span class="special">&amp;)</span> <span class="special">{</span> <span class="special">}</span>
+<span class="keyword">bool</span> <span class="identifier">f</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">good</span><span class="special">&amp;,</span> <span class="keyword">const</span> <span class="identifier">good</span><span class="special">&amp;)</span> <span class="special">{</span> <span class="keyword">return</span> <span class="keyword">true</span><span class="special">;</span> <span class="special">}</span>
 
 <span class="keyword">int</span> <span class="identifier">main</span><span class="special">()</span> <span class="special">{</span>
 	<span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span><span class="special">&lt;&lt;</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">boolalpha</span><span class="special">;</span>
diff --git a/doc/html/index/s11.html b/doc/html/index/s11.html
index 55d5c81..98bc5ae 100644
--- a/doc/html/index/s11.html
+++ b/doc/html/index/s11.html
@@ -24,7 +24,7 @@
 </div>
 <div class="section">
 <div class="titlepage"><div><div><h2 class="title" style="clear: both">
-<a name="id1124648"></a>Class Index</h2></div></div></div>
+<a name="id1192383"></a>Class Index</h2></div></div></div>
 <p><a class="link" href="s11.html#idx_id_0">A</a> <a class="link" href="s11.html#idx_id_2">C</a> <a class="link" href="s11.html#idx_id_3">D</a> <a class="link" href="s11.html#idx_id_4">E</a> <a class="link" href="s11.html#idx_id_5">F</a> <a class="link" href="s11.html#idx_id_6">H</a> <a class="link" href="s11.html#idx_id_7">I</a> <a class="link" href="s11.html#idx_id_8">M</a> <a class="link" href="s11.html#idx_id_9">N</a> <a class="link" href="s11.html#idx_id_10">O</a> <a class="link" href="s11.html#idx_id_11">P</a> <a class="link" href="s11.html#idx_id_12">R</a> <a class="link" href="s11.html#idx_id_13">T</a></p>
 <div class="variablelist"><dl class="variablelist">
 <dt>
diff --git a/doc/html/index/s12.html b/doc/html/index/s12.html
index e35106f..c1de26b 100644
--- a/doc/html/index/s12.html
+++ b/doc/html/index/s12.html
@@ -24,7 +24,7 @@
 </div>
 <div class="section">
 <div class="titlepage"><div><div><h2 class="title" style="clear: both">
-<a name="id1128255"></a>Typedef Index</h2></div></div></div>
+<a name="id1195400"></a>Typedef Index</h2></div></div></div>
 <p><a class="link" href="s12.html#idx_id_21">F</a> <a class="link" href="s12.html#idx_id_28">R</a> <a class="link" href="s12.html#idx_id_29">T</a> <a class="link" href="s12.html#idx_id_31">V</a></p>
 <div class="variablelist"><dl class="variablelist">
 <dt>
diff --git a/doc/html/index/s13.html b/doc/html/index/s13.html
index 12e43cb..7b8a852 100644
--- a/doc/html/index/s13.html
+++ b/doc/html/index/s13.html
@@ -24,7 +24,7 @@
 </div>
 <div class="section">
 <div class="titlepage"><div><div><h2 class="title" style="clear: both">
-<a name="id1128464"></a>Macro Index</h2></div></div></div>
+<a name="id1195591"></a>Macro Index</h2></div></div></div>
 <p><a class="link" href="s13.html#idx_id_33">B</a></p>
 <div class="variablelist"><dl class="variablelist">
 <dt>
diff --git a/doc/html/index/s14.html b/doc/html/index/s14.html
index d516966..fb56f32 100644
--- a/doc/html/index/s14.html
+++ b/doc/html/index/s14.html
@@ -23,7 +23,7 @@
 </div>
 <div class="section">
 <div class="titlepage"><div><div><h2 class="title" style="clear: both">
-<a name="id1130188"></a>Index</h2></div></div></div>
+<a name="id1196594"></a>Index</h2></div></div></div>
 <p><a class="link" href="s14.html#idx_id_48">A</a> <a class="link" href="s14.html#idx_id_49">B</a> <a class="link" href="s14.html#idx_id_50">C</a> <a class="link" href="s14.html#idx_id_51">D</a> <a class="link" href="s14.html#idx_id_52">E</a> <a class="link" href="s14.html#idx_id_53">F</a> <a class="link" href="s14.html#idx_id_54">H</a> <a class="link" href="s14.html#idx_id_55">I</a> <a class="link" href="s14.html#idx_id_56">M</a> <a class="link" href="s14.html#idx_id_57">N</a> <a class="link" href="s14.html#idx_id_58">O</a> <a class="link" href="s14.html#idx_id_59">P</a> <a class="link" href="s14.html#idx_id_60">R</a> <a class="link" href="s14.html#idx_id_61">T</a> <a class="link" href="s14.html#idx_id_62">U</a> <a class="link" href="s14.html#idx_id_63">V</a></p>
 <div class="variablelist"><dl class="variablelist">
 <dt>
diff --git a/doc/operators.qbk b/doc/operators.qbk
index 67b3f07..435c148 100644
--- a/doc/operators.qbk
+++ b/doc/operators.qbk
@@ -247,7 +247,11 @@ All traits are implemented the same way using preprocessor macros to avoid code
 duplication.
 The main files are in [^boost/type_traits/detail]: [^has_binary_operator.hpp],
 [^has_prefix_operator.hpp] and [^has_postfix_operator.hpp].
-The example of prefix `operator-` is presented below:
+
+Given a sufficiently conforming C++11 compiler, these traits are implemented in a rather
+compact and straightforward way that should always give accurate answers.
+
+In C++03 there is a legacy implementation, by way of example the prefix `operator-` is presented below:
 
 ``
 namespace boost {
@@ -416,11 +420,11 @@ struct has_unary_minus : ::boost::integral_constant<bool,(::boost::detail::has_u
 
 [heading Limitation]
 
-* Requires a compiler with working SFINAE.
+* Prior to C++11, requires a compiler with working SFINAE.
 
 [heading Known issues]
 
-* These traits cannot detect whether the operators are public or not:
+* Prior to C++11, these traits cannot detect whether the operators are public or not:
 if an operator is defined as a private member of type `T` then
 the instantiation of the corresponding trait will produce a compiler error.
 For this reason these traits cannot be used to determine whether a type has a
@@ -430,7 +434,7 @@ struct A { private: A operator-(); };
 boost::has_unary_minus<A>::value; // error: A::operator-() is private
 ``
 
-* There is an issue if the operator exists only for type `A` and `B` is
+* Prior to C++11, there is an issue if the operator exists only for type `A` and `B` is
 convertible to `A`. In this case, the compiler will report an ambiguous overload
 because both the existing operator and the one we provide (with argument of type
 `any`) need type conversion, so that none is preferred.