#include <iostream>
 
 
/**
 * @brief Constexpr class.
 */
class ConstValue
{
    private:
        // the value to store
        const int m_value;
 
    public:
        // explicit constructor
        constexpr explicit ConstValue(int value) :
            m_value(value)
        {
        }
        // explicit backconversion (for output etc.)
        constexpr explicit operator const int(void) 
        {
            return m_value;
        }
};
 
 
// global variable test
//
static constexpr const ConstValue VALUE = (ConstValue)1;   // works
static const int VALUEINT = (int)VALUE;                    // works
static const char* STRING = "STRING";                      // works
 
 
// class member global variable test
//
class Foo
{
    public:
        // static constant member variables
        static constexpr const ConstValue VALUE = (ConstValue)2;  // fails
        static const int VALUEINT = (int)VALUE;                   // works
        static constexpr const char* STRING = "Foo::STRING";      // fails
 
        // function access tests
        static const ConstValue value(void) {return VALUE;}       // fails
        static const int valueInt(void) {return (int)VALUE;}      // fails
        static const char* string(void) { return STRING; }        // fails
};
 
 
/**
 * @brief Main function.
 */
int main()
{
    // integer output
    std::cout << "VALUE = " << (int)VALUE << " (should be 1)\n";
    std::cout << "VALUEINT = " << VALUEINT << " (should be 1)\n";
    std::cout << "Foo::VALUE = " << (int)Foo::VALUE << " (should be 2)\n";
    std::cout << "Foo::VALUEINT = " << Foo::VALUEINT << " (should be 2)\n";
    std::cout << "Foo::value() = " << (int)Foo::value() << " (should be 2)\n";
    std::cout << "Foo::valueInt() = " << (int)Foo::valueInt() << " (should be 2)\n";
 
    // string output (beware of nullptrs)
    const char *ptr;
    ptr = STRING; std::cout << "STRING = " << (ptr?ptr:"<nullptr>") << " (should be STRING)\n";
    ptr = Foo::STRING; std::cout << "Foo::STRING = " << (ptr?ptr:"<nullptr>") << " (should be Foo::STRING)\n";
    ptr = Foo::string(); std::cout << "Foo::string() = " << (ptr?ptr:"<nullptr>") << " (should be Foo::STRING)\n";
 
    // done
    return 0;
}