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VS.NET - non-type template classes with FLOAT

Posted on 2003-11-12
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Last Modified: 2010-04-02
Hi,

I am having a problem compiling one of my projects (VS.NET, project imported from VC6), because there is a problem with how VS.NET handles FLOATS in non-type template classes. I have checked out MSDN : http://msdn.microsoft.com/library/default.asp?url=/library/en-us/vccore/html/C2993.asp BUT no joy as it says if it is a class template which mine is, there is no easy workaround.

So to my question, does anyone know of a way to solve this ? I am thinking that i will have to write a new class to include the float parameters only, and take them out of the template class. Is this the correct way ? For your info, below is my template class.

template<class T, TypeID_gem_t TypeID, T Invalid>
class CGEM_ArrayItem : public CGEM_DataItem
{      
      LPCSTR      m_pszName;
      T*            m_pVal;
      size_t      m_cElemCount;
      TypeID_gem_t m_type;

 public:
       CGEM_ArrayItem(const TGEM_DATA_DEF& DataDef)  
             : m_cElemCount(DataDef.ItemCount),

              m_type(TypeID)
      {
            m_pVal = new T[m_cElemCount];

            if(m_pVal == 0)
                  m_cElemCount = 0;
            else
                  for(int i = 0; i < m_cElemCount; i++)
                              m_pVal[i] = Invalid;

            m_pszName = ::_strdup(DataDef.pszItemName);

            TGEM_DATA d;
            d.val = DataDef.IniVal;
            d.ParType = DataDef.ParType;

            Set(d);
      }

      ~CGEM_ArrayItem()
      {
            delete[] m_pVal;
            
            ::free(m_pszName);
      }


      static SAFEARRAY* GetSafeArray(const TGEM_DATA& data)
      {
            switch(data.ParType)
            {
                  case GEM_I8_ARRAY:      return data.val.I8_array;
                  case GEM_I16_ARRAY:      return data.val.I16_array;                  
                  case GEM_I32_ARRAY:      return data.val.I32_array;
                  case GEM_I64_ARRAY:      return data.val.I64_array;

                  case GEM_SF_ARRAY:      return data.val.SF_array;      //singlefloat      
                  case GEM_DF_ARRAY:      return data.val.DF_array;      //doublefloat            

                  case GEM_U8_ARRAY:      return data.val.U8_array;                  
                  case GEM_U16_ARRAY:      return data.val.U16_array;                  
                  case GEM_U32_ARRAY:      return data.val.U32_array;                  
                  case GEM_U64_ARRAY:      return data.val.U64_array;                  
                  case GEM_B_ARRAY:      return data.val.B_array;                  

                  default:
                        ATLASSERT(false);
                        return NULL;
            }            
      }


      HRESULT Set(const TGEM_DATA& data)
      {
            HRESULT hr = E_INVALIDARG;
            SAFEARRAY *psa = GetSafeArray(data);

            if(psa != NULL)            
            {
                  ULONG size = sizeof T;
                  ATLASSERT(SafeArrayGetElemsize(psa) == sizeof T);
                  
                  void *pSrc;
                  hr = SafeArrayAccessData(psa, &pSrc);

                  if(SUCCEEDED(hr))
                  {
                        long plUbound;

                        hr = SafeArrayGetUBound(psa, 1, &plUbound);

                        if(SUCCEEDED(hr) && ++plUbound == m_cElemCount)
                              memcpy(m_pVal, pSrc, plUbound * sizeof T);
                        else
                              hr = E_INVALIDARG;

                        SafeArrayUnaccessData(psa);
                  }
            }
                  
            return hr;
      }
      


      TypeID_gem_t      GetType() { return m_type; }
      Data_gem_t*            GetData() { return m_pVal; }
      LPCSTR                  GetName() { return m_pszName; }
      Integer32_gem_t GetElementCount() { return m_cElemCount; }

      void Invalidate()
      {
            if(m_pVal)
            {                  
                  for(int i = 0; i < m_cElemCount; i++)
                  {
                        m_pVal[i] = 0;
                  }
            }
      }
};

Any help would be most appreciated in this porting exercise from VS6 to VS.NET C++.

Kind Regards
Jon.




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Question by:upliftin
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3 Comments
 
LVL 17

Accepted Solution

by:
rstaveley earned 200 total points
ID: 9734842
I think you have to pass it as a constructor parameter :-(

e.g.
--------8<--------
#include <iostream>

template<class T> class TC {
        const T initialiser;
public:
        TC(T initialiser) : initialiser(initialiser) {}
        void print() const { std::cout << "Initialiser is " << initialiser << '\n';}
};

int main()
{
        TC<double> tc(123.456);
        tc.print();
}
--------8<--------
0
 
LVL 9

Expert Comment

by:tinchos
ID: 10249035
No comment has been added lately, so it's time to clean up this TA.
I will leave the following recommendation for this question in the Cleanup topic area:

Accept: rstaveley {http:#9734842}

Please leave any comments here within the next seven days.
PLEASE DO NOT ACCEPT THIS COMMENT AS AN ANSWER!

Tinchos
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