NullValue.hh

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#ifndef __DIADES__UTILS__NULLVALUE__HH__
#define __DIADES__UTILS__NULLVALUE__HH__

namespace Diades
{
   namespace Utils
   {

      template<typename _Object>
      class AbstractNullValue
      {
      public:
         using Object = _Object;
         virtual Object nullValue() const = 0;

         bool operator()(const Object & object) const
         {
            return object == nullValue();
         }
      };

      template<typename _Object>
      class NullValue : public AbstractNullValue<_Object>
      {
      public:
         using Object = _Object;

         virtual Object
         nullValue() const
         {
            return Object();
         }
      };

      template<>
      class NullValue<std::string> : public AbstractNullValue<std::string>
      {
      public:

         virtual std::string
         nullValue() const
         {
            return "";
         }
      };

      template<>
      class NullValue<unsigned> : public AbstractNullValue<unsigned>
      {
      public:

         virtual unsigned
         nullValue() const
         {
            return std::numeric_limits<unsigned>::max();
         }
      };

      template<>
      class NullValue<size_t> : public AbstractNullValue<size_t>
      {
      public:

         virtual size_t
         nullValue() const
         {
            return std::numeric_limits<size_t>::max();
         }
      };
   }
}


#endif /* __DIADES__UTILS__NULLVALUE__HH__ */