_CLASS_REQUIRE for; Why not use BOOST_CLASS_REQUIRE?</span></div><div class="line"><a name="l00043"></a><span class="lineno">   43</span>&#160;<span class="comment">// TODO: What is gil_function_requires for; Why not function_requires?</span></div><div class="line"><a name="l00044"></a><span class="lineno">   44</span>&#160;</div><div class="line"><a name="l00045"></a><span class="lineno">   45</span>&#160;<span class="preprocessor">#ifdef BOOST_GIL_USE_CONCEPT_CHECK</span></div><div class="line"><a name="l