Implement empty_value

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();
+}