Question

Well I am attempting to make my way through developing an Excel Add-in. I am trying small functions with the sample code in Excel 2007 SDK as as a guide. I am having difficulty with attempting to display a double type data in Excel. Assuming the UDF is called DisplayDouble() when the sample code is executed and a call is placed with an argument of real type data such as DisplayDouble(12.3) the sample code works yet if I attempt to use an argument that references a real type data from cell such as DisplayDouble(A1) where cell A1 in the Excel worksheet has the value 12.3 the sample code does not work

You can see the sample code below this paragraph. Any hints will help me move along the learning ladder

_declspec(dllexport) LPXLOPER12 WINAPI DisplayDouble (LPXLOPER12 n)
{
  static XLOPER12 xResult;
  XLOPER12 xlt;
  int error = -1;
  double d;

  switch (n->xltype)
  {

  case xltypeNum:
        d = (double)n->val.num;
        if (max < 0)
              error = xlerrValue;
        xResult.xltype = xltypeNum;
        xResult.val.num = d;
        break;

  case xltypeSRef:
        error = Excel12f(xlCoerce, &xlt, 2, n, TempNum12(xltypeNum));

        if (!error)
        {
              error = -1;
              d = xlt.val.w;
              xResult.xltype = xltypeNum;
              xResult.val.num = d;
        }
        Excel12f(xlFree, 0, 1, &xlt);
        break;
  default:
        error = xlerrValue;
        break;
  }

  if ( error != - 1 )
  {
        xResult.xltype = xltypeErr;
        xResult.val.err = error;
  }

  //Word of caution - returning static XLOPERs/XLOPER12s is not thread safe
  //for UDFs declared as thread safe, use alternate memory allocation mechanisms
  return(LPXLOPER12) &xResult;
}

Answer 1

looks like you coerced the value to xltypeNum but are then taking the integer value, with d = xlt.val.w rather than d = xlt.val.num