helper.cpp

namespace helper
{
    // these expressions will be evaluated at compile time
    template <typename T>
    constexpr typename std::enable_if<!std::is_convertible<T, std::string>::value, std::string>::type
    to_string(const T &val) // cannot be converted directly thus we have to use type traits to determine if we can use to_string
    {
        return std::to_string(val);
    };

    template <typename T>
    constexpr typename std::enable_if<std::is_convertible<T, std::string>::value, std::string>::type
    to_string(const T &val) // converts to string directly
    {
        return val;
    };
}