Updated docs

doc/headers.html

@@ -80,6 +80,7 @@
       <li><a href="headers/facilities.html">facilities.hpp</a></li>
       <li>facilities/</li>
       <li class="ps"><a href="headers/facilities/apply.html">apply.hpp</a></li>
+      <li class="ps"><a href="headers/facilities/check_empty.html">check_empty.hpp</a></li>
       <li class="ps"><a href="headers/facilities/empty.html">empty.hpp</a></li>
       <li class="ps"><a href="headers/facilities/expand.html">expand.hpp</a></li>
       <li class="ps"><a href="headers/facilities/identity.html">identity.hpp</a></li>

doc/ref.html

@@ -45,6 +45,7 @@
       <li><a href="ref/bool.html">BOOL</a></li>
       <!-- C -->
       <li><a href="ref/cat.html">CAT</a></li>
+      <li><a href="ref/check_empty.html">CHECK_EMPTY</a></li>
       <li><a href="ref/comma.html">COMMA</a></li>
       <li><a href="ref/comma_if.html">COMMA_IF</a></li>
       <li><a href="ref/compl.html">COMPL</a></li>

doc/ref/variadic_opt.html

@@ -16,6 +16,19 @@ Expands to 1 if the __VA_OPT__ construct is supported, otherwise expands to 0.
   <dt>None<br>
 </dt>
 </dl>
+	<h4>Remarks</h4>
+		<div>
+			This macro only returns 1 if the compiler is compiling at its own C++20 level and
+			__VA_OPT__ is supported. It is possible for a compiler to support the __VA_OPT__
+			construct when not compiling at its own C++20 level, but this macro will return
+			0 in that case even if __VA_OPT__ is normally supported for that level. The reason
+			for this is that such a compiler may have a compiler switch, enforcing a strict
+			adherence to a particular C++ standard level, which	gives a warning or an error
+			if __VA_OPT__ is specified below the C++20 level, and the preprocessor library
+			wants to avoid that happening. Therefore the macro will only test to see whether
+			or not __VA_OPT__ is supported at the C++20 level, while otherwise always returning
+			0 for all lesser C++ standard levels.
+		</div>
 <h4>Requirements</h4>
 <div> <b>Header:</b> &nbsp;<a href="../headers/variadic/opt.html">&lt;boost/preprocessor/variadic/opt.hpp&gt;</a>
 </div>

test/Jamfile.v2

@@ -211,6 +211,7 @@ alias preprocessor_isempty : :
 alias preprocessor_isempty
   :   
        [ compile isempty.cpp ]
+       [ compile checkempty.cpp ]
        [ compile-fail isempty_variadic_standard_failure.cpp : <define>BOOST_PP_VARIADICS=1 ]
        [ compile-fail isempty_variadic_standard_failure2.cpp : <define>BOOST_PP_VARIADICS=1 ]
  ;