gets a single element of an MTensor of real type.
- Used in C/C++ code in a library function called from Mathematica.
- Uses the same numbering scheme as Mathematica parts, i.e. the first element is 1.
- The array is assumed to have length at least equal to the rank of .
- A nonzero error code value will be returned if the element does not exist, if is not an MTensor of real type.