add ext::less implementation handling unrelated types

alib2std/src/extensions/functional.hpp

@@ -26,8 +26,36 @@
 #include <functional>
+#include "type_traits.hpp"
+#include "typeindex.h"
+
 namespace ext {
+template < typename _Tp = void >
+struct less;
+
+template < typename _Tp >
+struct less : public std::binary_function < _Tp, _Tp, bool > {
+	bool operator ( ) ( const _Tp & __x, const _Tp & __y ) const {
+		return __x < __y;
+	}
+};
+
+template < >
+struct less < void > {
+	template < typename _Tp, typename _Up, typename std::enable_if < supports < std::less < > ( _Tp, _Up ) >::value >::type * = nullptr >
+	auto operator ( ) ( _Tp && __t, _Up && __u ) const noexcept ( noexcept ( std::forward < _Tp > ( __t ) < std::forward < _Up > ( __u ) ) ) -> decltype ( std::forward < _Tp > ( __t ) < std::forward < _Up > ( __u ) ) {
+		return std::forward < _Tp > ( __t ) < std::forward < _Up > ( __u );
+	}
+
+	template < typename _Tp, typename _Up, typename std::enable_if < ! supports < std::less < > ( _Tp, _Up ) >::value >::type * = nullptr >
+	bool operator ( ) ( _Tp &&, _Up && ) const noexcept {
+		return ext::type_index ( typeid ( _Tp ) ) < ext::type_index ( typeid ( _Up ) );
+	}
+
+	typedef std::__is_transparent is_transparent;
+};
+
 /**
  * \brief
  * Class extending the reference wrapper class from the standard library. Original reason is to allow its use with standard stream aggregation class.

alib2std/test-src/extensions/FunctionalTest.cpp

+#include "FunctionalTest.h"
+#include <alib/functional>
+
+CPPUNIT_TEST_SUITE_NAMED_REGISTRATION( FunctionalTest, "bits" );
+CPPUNIT_TEST_SUITE_REGISTRATION( FunctionalTest );
+
+void FunctionalTest::setUp() {
+}
+
+void FunctionalTest::tearDown() {
+}
+
+void FunctionalTest::testLess() {
+	ext::less < > test;
+	CPPUNIT_ASSERT ( test ( 1, 2 ) == true );
+	CPPUNIT_ASSERT ( test ( 1, 2. ) == true );
+	CPPUNIT_EXCLUSIVE_OR( test ( std::string ( "aa" ), 1 ), test ( 1, std::string ( "aa" ) ) );
+}

alib2std/test-src/extensions/FunctionalTest.h

+#ifndef FUNCTIONAL_TEST_H_
+#define FUNCTIONAL_TEST_H_
+
+#include <cppunit/extensions/HelperMacros.h>
+
+class FunctionalTest : public CppUnit::TestFixture
+{
+  CPPUNIT_TEST_SUITE( FunctionalTest );
+  CPPUNIT_TEST( testLess );
+  CPPUNIT_TEST_SUITE_END();
+
+public:
+  void setUp();
+  void tearDown();
+
+  void testLess();
+};
+
+#endif  // FUNCTIONAL_TEST_H_