Implement empty_value

test/Jamfile.v2

@@ -123,5 +123,8 @@ run to_address_test.cpp ;
 run exchange_test.cpp ;
 run exchange_move_test.cpp ;
 
+run empty_value_test.cpp ;
+run empty_value_size_test.cpp ;
+
 use-project /boost/core/swap : ./swap ;
 build-project ./swap ;

test/empty_value_size_test.cpp

@@ -0,0 +1,60 @@
+/*
+Copyright 2018 Glen Joseph Fernandes
+(glenjofe@gmail.com)
+
+Distributed under the Boost Software License, Version 1.0.
+(http://www.boost.org/LICENSE_1_0.txt)
+*/
+#include <boost/config.hpp>
+#if !defined(BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION)
+#include <boost/core/empty_value.hpp>
+#include <boost/core/lightweight_test.hpp>
+
+struct T1 { };
+
+struct S1
+    : boost::empty_value<T1, 0, true> { };
+
+struct T2 {
+    int value;
+};
+
+struct S2
+    : boost::empty_value<T1, 0, true>
+    , boost::empty_value<T2, 1, true> { };
+
+struct S3
+    : boost::empty_value<T1, 0, false>
+    , boost::empty_value<T2, 1, true> { };
+
+struct T3 { };
+
+struct S4
+    : boost::empty_value<T1, 0, true>
+    , boost::empty_value<T3, 1, true> { };
+
+struct S5
+    : boost::empty_value<T1, 0, false>
+    , boost::empty_value<T3, 1, false> { };
+
+struct S6
+    : boost::empty_value<T1, 0, true>
+    , boost::empty_value<T2, 1, true>
+    , boost::empty_value<T3, 2, true> { };
+
+int main()
+{
+    BOOST_TEST(sizeof(S1) == sizeof(T1));
+    BOOST_TEST(sizeof(S2) == sizeof(T2));
+    BOOST_TEST(sizeof(S3) > sizeof(T2));
+    BOOST_TEST(sizeof(S4) == sizeof(T1));
+    BOOST_TEST(sizeof(S5) > sizeof(T1));
+    BOOST_TEST(sizeof(S6) == sizeof(T2));
+    return boost::report_errors();
+}
+#else
+int main()
+{
+    return 0;
+}
+#endif

test/empty_value_test.cpp

@@ -0,0 +1,76 @@
+/*
+Copyright 2018 Glen Joseph Fernandes
+(glenjofe@gmail.com)
+
+Distributed under the Boost Software License, Version 1.0.
+(http://www.boost.org/LICENSE_1_0.txt)
+*/
+#include <boost/core/empty_value.hpp>
+#include <boost/core/lightweight_test.hpp>
+
+struct empty {
+    operator bool() const {
+        return false;
+    }
+    operator bool() {
+        return true;
+    }
+};
+
+class type {
+public:
+    type()
+        : value_(false) { }
+    explicit type(bool value)
+        : value_(value) { }
+    operator bool() const {
+        return value_;
+    }
+private:
+    bool value_;
+};
+
+void test_bool()
+{
+    const boost::empty_value<bool> v1(boost::empty_init_t(), true);
+    BOOST_TEST(v1.get());
+    boost::empty_value<bool> v2;
+    BOOST_TEST(!v2.get());
+    v2 = v1;
+    BOOST_TEST(v2.get());
+    v2.get() = false;
+    BOOST_TEST(!v2.get());
+}
+
+void test_empty()
+{
+    empty e;
+    const boost::empty_value<empty> v1(boost::empty_init_t(), e);
+    BOOST_TEST(!v1.get());
+    boost::empty_value<empty> v2;
+    BOOST_TEST(v2.get());
+    v2 = v1;
+    BOOST_TEST(v2.get());
+    v2.get() = empty();
+    BOOST_TEST(v2.get());
+}
+
+void test_type()
+{
+    const boost::empty_value<type> v1(boost::empty_init_t(), true);
+    BOOST_TEST(v1.get());
+    boost::empty_value<type> v2;
+    BOOST_TEST(!v2.get());
+    v2 = v1;
+    BOOST_TEST(v2.get());
+    v2.get() = type();
+    BOOST_TEST(!v2.get());
+}
+
+int main()
+{
+    test_bool();
+    test_empty();
+    test_type();
+    return boost::report_errors();
+}